Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2017	Mar. 06, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	Arbutus Biopharma Corp
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		55,070,037
Entity Public Float			$ 198,187,182
Amendment Flag	false
Entity Central Index Key	0001447028
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 54,292	$ 23,413
Short-term investments	72,060	107,146
Accounts receivable	402	273
Accrued revenue	128	128
Investment tax credits receivable	340	293
Prepaid expenses and other assets	2,144	1,311
Total current assets	129,366	132,564
Restricted investment	12,601	12,601
Long-term investments	0	0
Property and equipment	24,854	17,683
Less accumulated depreciation	(12,671)	(10,738)
Property and equipment, net of accumulated depreciation	12,183	6,945
Intangible assets	58,647	99,445
Goodwill	24,364	24,364
Total assets	237,161	275,919
Current liabilities:
Accounts payable and accrued liabilities	10,646	9,910
Deferred revenue	2,742	15
Liability-classified options	1,239	553
Warrants	0	107
Total current liabilities	14,627	10,585
Deferred revenue, net of current portion	0	0
Deferred rent and inducements, long term	693	0
Loan payable	12,001	12,001
Contingent consideration	10,424	9,065
Deferred tax liability	16,943	41,263
Total liabilities	54,688	72,914
Stockholders’ equity:
Issued and outstanding: 500,000 (December 31, 2016 - nil)	49,780	0
Common shares, authorized - unlimited number with no par value, Issued and outstanding: 55,060,662 (December 31, 2016 - 54,841,494)	876,108	867,393
Additional paid-in capital	42,840	36,543
Deficit	(738,070)	(652,746)
Accumulated other comprehensive loss	(48,185)	(48,185)
Total stockholders' equity	182,473	203,005
Total liabilities and stockholders' equity	$ 237,161	$ 275,919

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, shares issued	500,000	0
Preferred stock, shares outstanding	500,000	0
Preferred stock, shares authorized (in shares)	1,164,000	0
Common shares, par value (in USD per share)	$ 0	$ 0
Common shares, shares issued	55,060,662	54,841,494
Common shares, shares outstanding	55,060,662	54,841,494

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Collaborations and contracts	$ 682	$ 229	$ 11,712
Licensing fees, milestone and royalty payments	10,018	1,262	11,564
Total revenue	10,700	1,491	23,276
Expenses
Research, development, collaborations and contracts	62,676	61,253	51,505
General and administrative	16,129	39,438	26,438
Depreciation of property and equipment	2,027	1,092	589
Acquisition costs	0	0	9,656
Impairment of intangible assets	40,798	253,197	39,007
Impairment of goodwill	0	138,150	0
Total expenses	121,630	493,130	127,195
Loss from operations	(110,930)	(491,639)	(103,919)
Other income (losses)
Interest income	1,538	1,391	674
Interest expense	(261)	0	0
Foreign exchange gains	2,301	1,120	21,771
Gain on disposition of financial instrument	0	1,000	0
Decrease (increase) in fair value of warrant liability	(22)	530	3,341
Increase in fair value of contingent consideration	(1,359)	(1,568)	(770)
Total other income (losses)	2,197	2,473	25,016
Loss before income taxes	(108,733)	(489,166)	(78,903)
Deferred income tax recovery	24,320	105,002	16,185
Net loss	(84,413)	(384,164)	(62,718)
Accrual of coupon on convertible preferred shares	(911)	0	0
Net loss attributable to common shares	$ (85,324)	$ (384,164)	$ (62,718)
Net loss attributable to common shareholders, per share
Basic net loss per common share (in USD per share)	$ (1.56)	$ (7.24)	$ (1.38)
Diluted net loss per common share (in USD per share)	$ (1.56)	$ (7.24)	$ (1.38)
Weighted average number of common shares
Basic weighted average number of common shares (in shares)	54,723,272	53,074,401	45,462,324
Diluted weighted average number of common shares (in shares)	54,723,272	53,074,401	45,462,324
Other Comprehensive loss
Cumulative translation adjustment	$ 0	$ 0	$ (25,872)
Comprehensive loss	$ (84,413)	$ (384,164)	$ (88,590)

Consolidated Statement of Stockholders’ Equity - USD ($) $ in Thousands	Total	Convertible Preferred Shares	Common Stock	Additional paid-in capital	Deficit	Accumulated other comprehensive loss
Balance (in shares) at Dec. 31, 2014			22,438,169
Balance at Dec. 31, 2014	$ 88,035		$ 290,004	$ 26,208	$ (205,864)	$ (22,313)
Stock-based compensation	22,093		$ 16,687	5,406
Issuance of common shares pursuant to exercise of options (in shares)			640,457
Issuance of common shares pursuant to exercise of options	1,651		$ 4,186	(2,535)
Issuance of common shares pursuant to exercise of warrants (in shares)			18,750
Issuance of common shares pursuant to exercise of warrants	371		$ 371
Issuance of common shares in conjunction with the private offering, net of issuance costs (in shares)			7,500,000
Issuance of common shares in conjunction with the private offering, net of issuance costs	142,177		$ 142,177
Increase of equity instruments in conjunction with the acquisition of Arbutus Inc. (in shares)			23,973,315
Increase of equity instruments in conjunction with the acquisition of Arbutus Inc.	381,942		$ 380,815	1,127
Currency translation adjustment	(25,872)					(25,872)
Net loss	(62,718)				(62,718)
Balance (in shares) at Dec. 31, 2015			54,570,691
Balance at Dec. 31, 2015	547,679		$ 834,240	30,206	(268,582)	(48,185)
Stock-based compensation	38,162		$ 31,986	6,176
Reclassification of equity to liability stock option awards	(3,243)			(3,243)
Certain fair value adjustments to liability stock option awards	3,621			3,621
Issuance of common shares pursuant to exercise of options (in shares)			100,303
Issuance of common shares pursuant to exercise of options	258		$ 475	(217)
Issuance of common shares pursuant to exercise of warrants (in shares)			170,500
Issuance of common shares pursuant to exercise of warrants	692		$ 692
Currency translation adjustment	0
Net loss	(384,164)				(384,164)
Balance (in shares) at Dec. 31, 2016			54,841,494
Balance at Dec. 31, 2016	$ 203,005		$ 867,393	36,543	(652,746)	(48,185)
Issuance of Preferred Shares, net of issuance cost of $1,131,000 (in shares)	0
Accrual of coupon on Preferred Shares	$ 0	$ 911			(911)
Stock-based compensation	14,858		$ 7,972	6,886
Certain fair value adjustments to liability stock option awards	(540)			(540)
Issuance of common shares pursuant to exercise of options (in shares)			40,156
Issuance of common shares pursuant to exercise of options	213		$ 262	(49)
Issuance of common shares pursuant to exercise of warrants (in shares)			179,000
Issuance of common shares pursuant to exercise of warrants	481		$ 481
Currency translation adjustment	0
Net loss	(84,413)				(84,413)
Balance (in shares) at Dec. 31, 2017		500,000	55,060,650
Balance at Dec. 31, 2017	$ 182,473	$ 49,780	$ 876,108	$ 42,840	$ (738,070)	$ (48,185)
Issuance of Preferred Shares, net of issuance cost of $1,131,000 (in shares)	500,000	500,000
Issuance of Preferred Shares, net of issuance cost of $1,131,000	$ 48,869	$ 48,869

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING ACTIVITIES
Net loss for the period	$ (84,413)	$ (384,164)	$ (62,718)
Items not involving cash:
Deferred income taxes	(24,320)	(105,061)	(16,185)
Depreciation of property and equipment	2,027	1,092	589
Loss (gain) on sale of property and equipment	(3)	174	0
Unrealized foreign exchange gains	(2,374)	(1,003)	(21,966)
Change in fair value of warrant liability	22	(530)	(3,341)
Change in fair value of contingent consideration	1,359	1,568	770
Impairment of intangible assets	40,798	253,197	39,007
Impairment of goodwill	0	138,150	0
Net change in non-cash operating items:
Accounts receivable	(129)	735	628
Accrued revenue	0	0	349
Investment tax credits receivable	(47)	(47)	(188)
Prepaid expenses and other assets	(833)	(115)	159
Accounts payable and accrued liabilities	736	26	(2,489)
Deferred revenue	2,727	(1,066)	(13,090)
Deferred rent and inducements	693	0	0
Net cash used in operating activities	(48,640)	(57,885)	(56,382)
INVESTING ACTIVITIES
Disposition (acquisition) of investments	35,086	(82,551)	9,645
Acquisition of restricted investment	0	(12,601)	0
Cash acquired through acquisition	0	0	324
Proceeds from sale of property and equipment	3	25	0
Acquisition of property and equipment	(7,264)	(3,996)	(2,287)
Net cash provided by (used in) investing activities	27,825	(99,123)	7,682
FINANCING ACTIVITIES
Proceeds from loan payable	0	12,001	0
Proceeds from issuance of common shares, net of issuance costs	0	0	142,177
Proceeds from sale of Preferred Shares, net of issuance costs	48,869	0	0
Issuance of common shares pursuant to exercise of options	100	192	1,651
Issuance of common shares pursuant to exercise of warrants	353	445	42
Net cash provided by financing activities	49,322	12,638	143,870
Effect of foreign currency rate changes on cash and cash equivalents	2,372	1,004	(578)
Increase in cash and cash equivalents	30,879	(143,366)	94,592
Cash and cash equivalents, beginning of period	23,413	166,779	72,187
Cash and cash equivalents, end of period	54,292	23,413	166,779
Supplemental cash flow information
Acquisition of property and equipment not yet paid	0	1,057	0
Investment tax credits received	108	0	24
Acquisition of Arbutus Inc. net of cash acquired	0	0	381,618
Research, development, collaborations
Items not involving cash:
Stock-based compensation	9,236	11,155	7,869
General and administrative expenses
Items not involving cash:
Stock-based compensation	$ 5,881	$ 28,004	$ 14,224

Nature of Business and Future Operations	12 Months Ended
Nature of Business and Future Operations	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of business and future operations	Nature of business and future operations Arbutus Biopharma Corporation (the “Company” or “Arbutus”) is a biopharmaceutical business dedicated to discovering, developing, and commercializing a cure for patients suffering from chronic hepatitis B infection, a disease of the liver caused by the hepatitis B virus (“HBV”). To pursue our strategy of developing a curative combination regimen, we have assembled an HBV pipeline consisting of multiple drug candidates with differing and complementary mechanisms of action (MOA). The success of the Company is dependent on obtaining the necessary regulatory approvals to bring its products to market and achieve profitable operations. The continuation of the research and development activities and the commercialization of its products are dependent on the Company’s ability to successfully complete these activities and to obtain adequate financing through a combination of financing activities and operations. It is not possible to predict either the outcome of future research and development programs or the Company’s ability to continue to fund these programs in the future.

Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Significant accounting policies

Basis of presentation

Arbutus Biopharma Corporation was incorporated in Canada on October 6, 2005 as an inactive wholly owned subsidiary of Inex Pharmaceuticals Corporation (Inex). Pursuant to a “Plan of Arrangement” effective April 30, 2007, the business and substantially all of the assets and liabilities of Inex were transferred to the Company. The consolidated financial statements for all periods presented herein include the consolidated operations of Inex until April 30, 2007 and the operations of the Company thereafter.

The Company has two wholly-owned subsidiaries as at December 31, 2017: Arbutus Biopharma, Inc. (Arbutus Inc. formerly OnCore Biopharma, Inc.) and Protiva Biotherapeutics Inc. ("Protiva"). Protiva was acquired on May 30, 2008. Arbutus Inc. was acquired by way of a Merger Agreement on March 4, 2015. On January 1, 2018, Protiva was amalgamated with Arbutus Biopharma Corporation.

In addition to Arbutus Inc. and Protiva, the Company's former wholly-owned subsidiary, Protiva Agricultural Development Company Inc. ("PADCo"), was previously recorded by the Company using the equity method. On March 4, 2016, Monsanto exercised its option to acquire 100% of the outstanding shares of PADCo, as described in note 4(d).

These consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Arbutus Inc. and Protiva. All intercompany transactions and balances have been eliminated on consolidation.

Recast of Comparative Financial Statements

Certain comparative figures in the Statements of Operations and Comprehensive Loss, Stockholders' Equity, and Cash Flows have been recast to decrease revenues and decrease cumulative translation loss adjustment by $1,597,000, due to translation adjustments from the Company's Canadian dollar functional currency to the U.S. dollar reporting currency for the year-ended December 31, 2015. The cumulative effect of the adjustment has been reflected in the Consolidated Balance Sheets for the year-ended December 31, 2016 as an increase in Deficit and decrease in Accumulated Other Comprehensive Income of $1,597,000. The recast had no effect on operating cash flows for fiscal 2015, 2016, and 2017. As of January 1, 2016, the Company's functional and reporting currency is the U.S. dollar, as described below.

Foreign currency translation and functional currency conversion

Prior to January 1, 2016, the Company's functional currency was the Canadian dollar. Translation gains and losses from the application of the U.S. dollar as the reporting currency during the period that the Canadian dollar was the functional currency are included as part of cumulative currency translation adjustment, which is reported as a component of shareholders' equity under accumulated other comprehensive loss.

The Company re-assessed its functional currency and determined as at January 1, 2016, its functional currency changed from the Canadian dollar to the U.S. dollar based on management's analysis of changes in the primary economic environment in which the Company operates. The change in functional currency is accounted for prospectively from January 1, 2016 and financial statements prior to and including the period ended December 31, 2015 have not been restated for the change in functional currency.

For periods commencing January 1, 2016, monetary assets and liabilities denominated in foreign currencies are translated into U.S. dollars using exchange rates in effect at the balance sheet date. Opening balances related to non-monetary assets and liabilities are based on prior period translated amounts, and non-monetary assets and non-monetary liabilities incurred after January 1, 2016 are translated at the approximate exchange rate prevailing at the date of the transaction. Revenue and expense transactions are translated at the approximate exchange rate in effect at the time of the transaction. Foreign exchange gains and losses are included in the statement of operations and comprehensive loss as foreign exchange gains.

Use of estimates

The preparation of the consolidated financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions about future events that affect the reported amounts of assets, liabilities, revenue, expenses, contingent assets and contingent liabilities as at the end or during the reporting period. Actual results could significantly differ from those estimates. Significant areas requiring the use of management estimates relate valuation of intangible assets and goodwill, recognition of revenue, stock-based compensation, and financial instruments, and the amounts recorded as accrued liabilities, contingent consideration, and income tax recovery.

Cash and cash equivalents

Cash and cash equivalents are all highly liquid instruments with an original maturity of three months or less when purchased. Cash equivalents are recorded at cost plus accrued interest. The carrying value of these cash equivalents approximates their fair value.

Short-term investments

Short-term investments have original maturities exceeding three months, and have remaining maturities less than one year. Short-term investments accrue interest daily based on a fixed interest rate for the term. The carrying value of these investments are recorded at cost plus accrued interest, which approximates their fair value. All investments are governed by the Board approved Investment Policy for the Company.

Loan payable and restricted investment

The Company obtained a loan from Wells Fargo for the purpose of financing its operations, including the expansion of laboratory facilities for its U.S. operations. The loan accrues interest daily based on an interest rate with a variable and fixed component. The variable component is the one-month London Interbank Offered Rate (LIBOR), and the fixed component is a margin based on the amount of collateral cash the Company maintains with the lender - see note 9. The loan is due December 2019. The loan is recorded at amortized cost.

The Company must maintain a cash or investment balance as collateral for the loan payable to Wells Fargo. The cash or investment is restricted from the Company's use until the loan is repaid. The Company does not expect to repay the loan within twelve months of the balance sheet date so has classified the restricted investment as a long-term asset. The restricted cash balance has been used to purchase a two year investment maturing on December 23, 2018 and accruing interest at a fixed interest rate of 1.25%. The carrying value of the restricted investment is recorded at cost plus any accrued interest not yet received, which approximates its fair value.

Fair value of financial instruments

We measure certain financial instruments and other items at fair value.

To determine the fair value, we use the fair value hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use to value an asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs based on assumptions about the factors market participants would use to value an asset or liability. The three levels of inputs that may be used to measure fair value are as follows:


•	Level 1 inputs are quoted market prices for identical instruments available in active markets.


•	Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability either directly or indirectly. If the asset or liability has a contractual term, the input must be observable for substantially the full term. An example includes quoted market prices for similar assets or liabilities in active markets.


•	Level 3 inputs are unobservable inputs for the asset or liability and will reflect management’s assumptions about market assumptions that would be used to price the asset or liability.

Assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurements. Changes in the observability of valuation inputs may result in a reclassification of levels for certain securities within the fair value hierarchy.

The Company’s financial instruments consist of cash and cash equivalents, short-term, and restricted investments, accounts receivable, accounts payable and accrued liabilities, warrants, and loan payable . Restricted investments approximate fair value due to the interest rates being at prevailing market rates.

The carrying values of cash and cash equivalents, short-term investments, accounts receivable and accounts payable and accrued liabilities approximate their fair values due to the immediate or short-term maturity of these financial instruments.

As quoted prices for the warrants are not readily available, the Company has used a Black-Scholes pricing model, as described in note 6, to estimate fair value. These are level 3 inputs as defined above.

To determine the fair value of the contingent consideration, the Company uses a probability weighted assessment of the likelihood the milestones would be met and the estimated timing of such payments, and then the potential contingent payments were discounted to their present value using a probability adjusted discount rate that reflects the early stage nature of the development program, time to complete the program development, and overall biotech indices, as detailed in note 10. The Company determined the fair value of the contingent consideration was $10,424,000 and the increase of $1,359,000 has been recorded in other losses in the statement of operations and comprehensive loss for the year ended December 31, 2017. The assumptions used in the discounted cash flow model are level 3 inputs as defined above.

The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation techniques used to determine such fair value:



	Level 1		Level 2	Level 3	December 31, 2017
Assets
Cash and cash equivalents	$	54,292	—	—	$	54,292
Short-term investments	72,060		—	—	72,060
Restricted investment	12,601		—	—	12,601
Total	$	138,953	—	—	$	138,953
Liabilities
Liability-classified stock option awards	—		—	1,239	1,239
Contingent consideration	—		—	10,424	10,424
Total	—		—	11,663	$	11,663



	Level 1		Level 2	Level 3		December 31, 2016
Assets
Cash and cash equivalents	$	23,413	—	—		$	23,413
Guaranteed investment certificates	107,146		—	—		107,146
Term deposit	12,601		—	—		12,601
Total	$	143,160	—	—		$	143,160
Liabilities
Warrants	—		—	$	107	$	107
Liability-classified stock option awards				553		553
Contingent consideration	—		—	9,065		9,065
Total	—		—	$	9,725	$	9,725

The following table presents the changes in fair value of the Company’s warrants:



	Liability at beginning of the period		Fair value of warrants exercised in the period			Increase (decrease) in fair value of warrants			Foreign exchange loss			Liability at end of the period
Year ended December 31, 2015	$	5,099	$	(334	)	$	(3,341	)	$	(541	)	$	883
Year ended December 31, 2016	$	883	$	(247	)	$	(529	)	$	—		$	107
Year ended December 31, 2017	$	107	$	(129	)	$	22		$	—		$	—

The following table presents the changes in fair value of the Company’s liability-classified stock option awards:



	Liability at beginning of the period		Reclassification of equity to liability ⁽¹⁾		Fair value of liability-classified stock option awards exercised in the period			Increase (decrease) in fair value of liability			Liability at end of the period
Year ended December 31, 2016	$	—	$	1,909	$	(54	)	$	(1,302	)	$	553
Year ended December 31, 2017	$	553	$	—	$	(103	)	$	789		$	1,239

(1) Upon functional currency conversion on January 1, 2016 - see functional currency conversion above.

The following table presents the changes in fair value of the Company’s contingent consideration:



	Contingent consideration at beginning of the period		Increase in fair value of contingent consideration		Contingent consideration at end of the period
Year ended December 31, 2015⁽¹⁾	$	6,727	$	770	$	7,497
Year ended December 31, 2016	$	7,497	$	1,568	$	9,065
Year ended December 31, 2017	$	9,065	$	1,359	$	10,424

(1) As at acquisition date of March 4, 2015.

Property and equipment

Property and equipment is recorded at cost less impairment losses, accumulated depreciation, related government grants and investment tax credits. The Company records depreciation using the straight-line method over the estimated useful lives of the capital assets as follows:



	Useful life (years)
Laboratory equipment		5
Computer and office equipment	2	—	5
Furniture and fixtures		5

Leasehold improvements are depreciated over their estimated useful lives but in no case longer than the lease term, except where lease renewal is reasonably assured.

If there is a major event indicating that the carrying value of property and equipment may be impaired then management will perform an impairment test and if the carrying value exceeds the recoverable value, based on undiscounted future cash flows, then such assets are written down to their fair values.

Goodwill and intangible assets

The costs incurred in establishing and maintaining patents for intellectual property developed internally are expensed in the period incurred.

Intangible assets consist of in-process research and development arising from the Company’s acquisition of Arbutus Inc. in 2015. In-process research and development (IPR&D) intangible assets are classified as indefinite-lived and are not amortized. IPR&D becomes definite-lived upon the completion or abandonment of the associated research and development efforts. Intangible assets with finite useful lives are amortized on a straight-line basis over their estimated useful lives, which are the respective patent terms. Amortization begins when intangible assets with finite lives are put into use. If there is a major event indicating that the carrying value of intangible assets may be impaired, then management will perform an impairment test in an interim period and if the carrying value exceeds the recoverable value, based on discounted future cash flows, then such assets are written down to their fair values.

The Company reviews the recoverable amount of intangible assets and goodwill on an annual basis, and the annual evaluation is performed as of December 31 each year. In addition, the Company evaluates for events or changes in the business that could indicate impairment and earlier testing. Such indicators include, but are not limited to, on an ongoing basis: (a) industry and market considerations such as increased competitive environment or adverse change in legal factors including an adverse assessment by regulators; (b) an accumulation of costs significantly in excess of the amount originally expected for the development of the asset; (c) current period operating or cash flow loss combined with a history of operating or cash flow losses or a projection or forecast that demonstrates continuing losses associated with the use of the asset; (d) adverse research and development program results; and (e) if applicable, a sustained decrease in share price.

Goodwill represents the excess of purchase price over the value assigned to the net tangible and identifiable intangible assets of Arbutus Inc. - see note 3. Goodwill has an indefinite accounting life and is therefore not amortized. Instead, goodwill is assessed for impairment on an annual basis, unless the Company identifies impairment indicators that would require earlier testing. For the period ended December 31, 2017, the Company has elected to early adopt ASU 2017-04, which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test, which required a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. All other goodwill impairment guidance remains substantially unchanged, and management continues to have the ability to perform a qualitative assessment to determine if a quantitative impairment test is necessary. The Company performs its qualitative analysis using factors including but not limited to: (a) macroeconomic conditions; (b) industry and market considerations; (c) cost factors; (d) overall financial performance; (e) other relevant entity-specific events; (f) events affecting a reporting unit; and (g) if applicable, a sustained decrease in share price in absolute terms and relative to peers. The qualitative assessment for the period ended December 31, 2017 did not indicate an impairment of goodwill and no further quantitative assessment was necessary.

Revenue recognition

The Company earns revenue from research and development collaboration and contract services, licensing fees, milestone and royalty payments. In arrangements with multiple deliverables, the delivered item or items is considered a separate unit of accounting if: (1) the delivered item has value to the customer on a standalone basis; and (2) if the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item is considered probably and substantially in the Company's control. If the elements of the arrangement do not meet both of the criteria above, they are recognized as a single unit of accounting. If the elements do meet the criteria above, arrangement consideration is allocated to the separate units of accounting based on their relative selling price. Non-refundable payments received under collaborative research and development agreements are recorded as revenue as services are performed and related expenditures are incurred. Non-refundable upfront license fees from collaborative licensing and development arrangements are recognized as the Company fulfills its obligations related to the various elements within the agreements, in accordance with the contractual arrangements with third parties and the term over which the underlying benefit is being conferred. If non-refundable license fees have values to the customer on a standalone basis, separate from the undelivered performance obligations, they are recognized upon delivery. To date, the Company has not recognized any non-refundable license fees upon delivery.

The Company evaluates new arrangements for any substantive milestones by considering: whether substantive uncertainty exists upon execution of the arrangement; if the event can only be achieved based in whole or in part on the Company’s performance, or occurrence of a specific outcome resulting from the Company’s performance; any future performance required, and payment is reasonable relative to all deliverables; and, the payment terms in the arrangement. Payments received upon the achievement of substantive milestones are recognized as revenue in their entirety. Payments received upon the occurrence of milestones that are non-substantive are deferred and recognized as revenue over the estimated period of performance applicable to the associated collaborative agreement.

Revenue earned under research and development manufacturing collaborations where the Company bears some or all of the risk of a product manufacturing failure is recognized when the purchaser accepts the product and there are no remaining rights of return.

Revenue earned under research and development collaborations where the Company does not bear any risk of product manufacturing failure is recognized in the period the work is performed. For contracts where the manufacturing amount is specified, revenue is recognized as product is manufactured in proportion to the total amount specified under the contract.

Cash or other compensation received in advance of meeting the revenue recognition criteria is recorded on the balance sheet as deferred revenue. Revenue meeting recognition criteria but not yet received or receivable is recorded on the balance sheet as accrued revenue.

Leases and lease inducements

Leases entered into are classified as either capital or operating leases. Leases which substantially transfer all benefits and risks of ownership of property to the Company are accounted for as capital leases. At the time a capital lease is entered into, an asset is recorded together with its related long-term obligation to reflect the purchase and financing.

All other leases are accounted for as operating leases wherein rental payments are expensed as incurred.

Lease inducements represent leasehold improvement allowances and reduced or free rent periods and are amortized on a straight-line basis over the term of the lease and are recorded as a reduction of rent expense.

Research and development costs

Research and development costs, including acquired in-process research and development expenses for which there is no alternative future use, are charged as an expense in the period in which they are incurred.

Net loss attributable to common shareholders per share

The Company follows the two-class method when computing net loss attributable to common shareholders per share as the Company has issued Preferred Shares (note 6) that meet the definition of participating securities. The Preferred Shares entitle the holders to participate in dividends but do not require the holders to participate in losses of the Company. Accordingly, if the Company reports a net loss attributable to common shareholders net losses are not allocated to Preferred Shareholders.

Net loss attributable to common shareholders per share is calculated based on the weighted average number of common shares outstanding. Diluted net loss attributable to common shareholders per share does not differ from basic net loss attributable to common shareholders per share for the years ended December 31, 2017, 2016 and 2015, since the effect of the Company’s stock options and warrants is anti-dilutive.

The following table sets out the computation of basic and diluted net loss attributable to common shareholders per share:



	For the year ended December 31
	2017					2016			2015
Numerator:	Common Shares			Preferred Shares		Common Shares			Common Shares
Allocation of distributable earnings	$	—		$	911	$	—		$	—
Allocation of undistributed earnings (loss)	(85,324		)	—		(384,164		)	(62,718		)
Allocation of earnings (loss) attributed to shareholders	$	(85,324	)	$	911	$	(384,164	)	$	(62,718	)
Denominator:
Weighted average number of shares - basic and diluted	54,723,272			104,110		53,074,401			45,462,324
Basic and diluted net loss attributable to shareholders per share	$	(1.56	)	$	8.75	$	(7.24	)	$	(1.38	)

For the year ended December 31, 2017, potential common shares of 12,521,550 were excluded from the calculation of income per common share because their inclusion would be anti-dilutive (December 31, 2016 – 4,645,864; December 31, 2015 – 2,899,331). On January 12, 2018 a further 664,000 preferred shares were issued (see note 6), which increased the total potential common shares excluded from the calculation of income per common share to 21,878,002 as at that date.

Government grants and refundable investment tax credits

Government grants and tax credits provided for current expenses are included in the determination of income or loss for the year, as a reduction of the expenses to which they relate.

Deferred income taxes

Income taxes are accounted for using the asset and liability method of accounting. Deferred income taxes are recognized for the future income tax consequences attributable to differences between the carrying values of assets and liabilities and their respective income tax bases and for loss carry-forwards. Deferred income tax assets and liabilities are measured using enacted income tax rates expected to apply to taxable income in the periods in which temporary differences are expected to be recovered or settled. The effect on deferred income tax assets and liabilities of a change in tax laws or rates is included in earnings in the period that includes the enactment date. When realization of deferred income tax assets does not meet the more-likely-than-not criterion for recognition, a valuation allowance is provided.

Equity classified stock option awards

The Company grants stock options to employees, directors and consultants pursuant to share incentive plans described in note 6. Compensation expense is recorded for issued stock options using the fair value method with a corresponding increase in additional paid-in capital. Any consideration received on the exercise of stock options is credited to share capital.

The fair value of equity classified stock options is measured at the grant date and amortized on a straight-line basis over the vesting period.

Liability-classified stock option awards

The Company accounts for liability-classified stock option awards ("liability options") under ASC 718 - Compensation - Stock Compensation ("ASC 718"), under which awards of options that provide for an exercise price that is not denominated in: (a) the currency of a market in which a substantial portion of the Company's equity securities trades, (b) the currency in which the employee's pay is denominated, or (c) the Company's functional currency, are required to be classified as liabilities. Due to the change in functional currency as of January 1, 2016, certain stock option awards with exercise prices denominated in Canadian dollars changed from equity classification to liability classification. As such, the historic equity classification of these stock option awards changed to liability classification effective January 1, 2016. The change in classification resulted in reclassification of these awards from additional paid-in capital to liability-classified options.

Liability options are re-measured to their fair values at each reporting date with changes in the fair value recognized in share-based compensation expense or additional paid-in capital until settlement or cancellation. Under ASC 718, when an award is reclassified from equity to liability, if at the reclassification date the original vesting conditions are expected to be satisfied, then the minimum amount of compensation cost to be recognized is based on the grant date fair value of the original award. Fair value changes below this minimum amount are recorded in additional paid-in capital.

Replacement awards

Replacement awards are share-based payment awards exchanged for awards held by employees of Arbutus Inc. As part of the Company’s acquisition of Arbutus Inc., Arbutus shares were exchanged for Arbutus Inc.’s shares subject to repurchase rights held by Arbutus Inc.’s employees.

As at the date of acquisition of Arbutus Inc., the Company determined the total fair value of replacement awards and attributed a portion of the replacement awards to pre-combination service as part of the total acquisition consideration, and a portion to post-combination service, which is recognized as compensation expense over the expiry period of repurchase provision rights subsequent to the acquisition date.

The replacement awards consist of common shares that were issued at acquisition. Accordingly, as stock compensation expense related to these awards is recognized, share capital is increased by a corresponding amount. Replacement awards are excluded in the calculation of basic net income (loss) per common share until the repurchase rights have expired.

Warrants

The Company accounts for the warrants under the authoritative guidance on accounting for derivative financial instruments indexed to, and potentially settled in, a company’s own stock, on the understanding that in compliance with applicable securities laws, the registered warrants require the issuance of registered securities upon exercise and do not sufficiently preclude an implied right to net cash settlement. The Company classifies warrants in its consolidated balance sheet as a liability which is revalued at each balance sheet date subsequent to the initial issuance. The Company uses the Black-Scholes pricing model to value the warrants. Determining the appropriate fair-value model and calculating the fair value of registered warrants requires considerable judgment. A small change in the estimates used may cause a relatively large change in the estimated valuation. The estimated volatility of the Company’s common stock at the date of issuance, and at each subsequent reporting period, is based on historic fluctuations in the Company’s stock price. The risk-free interest rate is based on the Government of Canada rate for bonds with a maturity similar to the expected remaining life of the warrants at the valuation date. The expected life of the warrants is based on the historical pattern of exercises of warrants.

Preferred Shares

The Company accounts for Preferred Shares under ASC 480, which provides guidance for equity instruments with conversion features. The Company classifies Preferred Shares in its consolidated balance sheet wholly as equity, with no bifurcation of conversion feature from the host contract, given that the Preferred Shares cannot be cash settled and the redemption features, which include a fixed conversion ratio with predetermined timing and proceeds, are within the Company's control. The Company accrues for the 8.75% per annum compounding accrual at each reporting period end date as an increase to share capital, and an increase to deficit (see note 6).

Segment information

The Company operates in a single reporting segment. Substantially all of the Company’s revenues to date were earned from customers or collaborators based in the United States. Substantially all of the Company’s premises, property and equipment are located in Canada and the United States.

Recent accounting pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued standards that are not yet effective will not have a material impact on our financial position or results of operations upon adoption.

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (ASC 606). The standard, as subsequently amended (ASU 2015-14, ASU 2016-08, ASU 2016-10, ASU 2016-12, ASU 2016-20), is intended to clarify the principles for recognizing revenue and to develop a common revenue standard for U.S. GAAP and IFRS by creating a new Topic 606, Revenue from Contracts with Customers. This guidance supersedes the revenue recognition requirements in ASC 605, Revenue Recognition, and supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition – Construction-Type and Production-Type Contracts. The core principle of the accounting standard is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those good or services. The amendments should be applied by either (1) retrospectively to each prior reporting period presented; or (2) retrospectively with the cumulative effect of initially applying this ASU recognized at the date of initial application. The new guidance is effective for fiscal years beginning after December 15, 2017, which for the Company means January 1, 2018. The Company will be applying the modified retrospective method for its implementation. Based on its evaluation, the Company believes that there will be no quantitative impact on its consolidated financial statements, but there will be disclosure changes mostly related to the timing and recognition of licensing and collaboration contracts that are described in note 4.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842): Recognition and Measurement of Financial Assets and Financial Liabilities. The update supersedes Topic 840, Leases and requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous GAAP. Topic 842 retains a distinction between finance leases and operating leases, with cash payments from operating leases classified within operating activities in the statement of cash flows. The amendments in this update are effective for fiscal years beginning after December 15, 2018 for public business entities, which for the Company means January 1, 2019. The Company does not plan to early adopt this update. The extent of the impact of this adoption has not yet been determined.

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The update addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice. Under this update, the classification of cash receipts and payments that have aspects of more than one class of cash flows should be determined first by applying specific guidance in GAAP. In the absence of specific guidance, an entity should determine each separately identifiable source or use within the cash receipts and cash payments on the basis of the nature of the underlying cash flows. An entity should then classify each separately identifiable source or use within the cash receipts and payments on the basis of their nature in financing, investing, or operating activities. In situations in which cash receipts and payments have aspects of more than one class of cash flows and cannot be separated by source or use, the appropriate classification should depend on the activity that is likely to be the predominant source or use of cash flows for the item. The amendments in this update are effective for public business entities for fiscal years beginning after December 31, 2017, which for the Company means January 1, 2018, and interim periods within those fiscal years. Early adoption is permitted. The amendments in this update should be applied using a retrospective transition method to each period presented. If it is impracticable to apply the amendments retrospectively for some of the issues, the amendments for those issues would be applied prospectively as of the earliest date practicable. The Company is currently evaluating the extent of the impact of this adoption.

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Statement of Cash Flows: Restricted Cash. The update requires the statement of cash flows to explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2017, which for the Company means January 1, 2018. Early adoption is permitted, including adoption in an interim period. If an entity early adopts the amendments in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that included that interim period. The amendments in this update should be applied using a retrospective transition method to each period presented. The Company does not expect the extent of the impact of this adoption to be significant.

In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting. The amendments in this Update provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under Topic 718. An entity should account for effects of a modification unless all of the following are met: (1) the fair value of the modified award is the same as the fair value of the original award immediately before the original award is modified; (2) the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; (3) the classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. The amendments in this Update are effective for all entities for annual periods and interim periods within those annual periods, beginning after December 15, 2017, which for the Company means January 1, 2018. Early adoption is permitted, including adoption in any interim period for public business entities for reporting periods for which financial statements have not yet been issued. The amendments in this Update should be applied prospectively to an award modified on or after the adoption date. The Company early adopted the amendments in this Update effective April 1, 2017. This adoption did not have a material effect on the Company's statement of operations and comprehensive loss for the period beginning on the adoption date, to the period ended December 31, 2017, as no significant award modifications occurred.

Impairment Evaluations For Intangible Assets and Goodwill

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Impairment evaluations for intangible assets and goodwill

All in-process research and development (IPR&D) acquired is currently classified as indefinite-lived and is not currently being amortized. IPR&D becomes definite-lived upon the completion or abandonment of the associated research and development efforts, and will be amortized from that time over an estimated useful life based on respective patent terms. The Company evaluates the recoverable amount of intangible assets on an annual basis and performs an annual evaluation of goodwill as of December 31 each year, unless there is an event or change in the business that could indicate a requirement to test at an interim period.

Impairment of intangible assets

During the year-ended December 31, 2017, the Company recorded a total impairment charge of $40,798,000 for the discontinuance of the STING agonists. This charge represents the remaining value of the acquired Immune Modulator drug class. In addition, the Company recorded an income tax benefit of $16,926,000 corresponding to the impairment charge - see note 8.

At December 31, 2016, the Company re-assessed the discount rate used in its valuation models used to assess the carrying value of goodwill and intangible assets for impairment as a result of the sustained discrepancy between the Company’s market capitalization compared to carrying values and management’s assessment of fair values. The change in discount rate resulted in an impairment charge of $96,873,000 to the Company’s intangible assets at December 31, 2016.

The following table summarizes the carrying values, net of impairment of the intangible assets as at December 31, 2017:



Year ended December 31	2017		2016
IPR&D – Immune Modulators	—		40,798
IPR&D – Antigen Inhibitors	14,811		14,811
IPR&D – cccDNA Sterilizers	43,836		43,836
Total IPR&D	$	58,647	$	99,445

Annual impairment evaluation of goodwill

Goodwill was recorded as a result of the acquisition of Arbutus Inc. as described in note 2. As part of the evaluation of the recoverability of goodwill, the Company has identified only one reporting unit to which the total carrying amount of goodwill has been assigned. The Company performs its annual impairment evaluation of goodwill on December 31.

The Company determines the fair value of the reporting unit using accepted valuation methods, including the use of discounted cash flows supplemented by market-based assessments of fair value. The income approach is used for the quantitative assessment to estimate the fair value of the reporting unit, which requires estimating future cash flows and risk-adjusted discount rates in the Company's discounted cash flow model. The overall market outlook and cash flow projections of the reporting unit involves the use of key assumptions, including cash flows, discount rates and probability of success. Due to uncertainties in the estimates that are inherent to the Company's industry, actual results could differ significantly from the estimates made. Many key assumptions in the cash flow projections are interdependent on each other. A change in any one or combination of these assumptions could impact the estimated fair value of the reporting unit. See note 2 for additional discussion of the Company's policy for accounting for goodwill.

As at December 31, 2016, the Company re-assessed the discount rate used in the calculation of fair value, consistent with the change to the discount rate used in the intangible assets impairment assessment (described above). As a result of the increased discount rate, the carrying value of the reporting unit determined in step one of the impairment assessment exceeded the fair value of the reporting unit, and as such the Company proceeded to the second step of the impairment test, which measures the amount of an impairment charge. In the second step, the carrying value of goodwill is compared to the fair value of goodwill that is implied by performing a hypothetical purchase price allocation based on identifiable assets at the date of the assessment. The remaining implied goodwill of $24,364,000 is the result of deferred taxes in the hypothetical purchase price allocation. As a result, the Company recorded an impairment for $138,150,000 against goodwill for the year ended December 31, 2016.

For the period ended December 31, 2017, the Company has elected to early adopt ASU 2017-04 (as described in note 2 above). On December 31, 2017, the Company conducted its annual impairment evaluation of goodwill and performed a comprehensive qualitative analysis using factors including but not limited to: (a) macroeconomic conditions; (b) industry and market considerations; (c) cost factors; (d) overall financial performance; (e) other relevant entity-specific events; (f) events affecting a reporting unit; and (g) if applicable, a sustained decrease in share price in absolute terms and relative to peers. The qualitative assessment did not indicate an impairment of goodwill and no further quantitative assessment was necessary.

The Company determines the fair value of the reporting unit each reporting period using accepted valuation methods, including the use of discounted cash flows supplemented by market-based assessments of fair value.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Collaborations, Contracts and Licensing Agreements

12 Months Ended

Dec. 31, 2017

Deferred Revenue Disclosure [Abstract]

Collaborations, contracts and licensing agreements

The following tables set forth revenue recognized under collaborations, contracts and licensing agreements:



	Year ended December 31
	2017		2016		2015
Alexion (a)	$	7,956	$	—	$	—
Gritstone (b)	2,499		—		—
Dicerna (c)	—		1,295		2,873
Monsanto (d)	—		—		13,384
DoD (e)	—		—		6,764
Other milestone and royalty payments (f)	245		196		255
Total revenue	$	10,700	$	1,491	$	23,276

The following table sets forth deferred collaborations and contracts revenue:



	December 31, 2017		December 31, 2016
Gritstone (b)	$	2,727	$	—
DoD (e)	15		15
Deferred revenue, current portion	2,742		15
Total deferred revenue	$	2,742	$	15

(a) License Agreement with Alexion

On March 16, 2017, the Company signed a license agreement with Alexion that entitles Alexion to research, develop, manufacture, and commercialize products with the Company's LNP technology in their single orphan disease target. In consideration for the rights granted under the agreement, the Company received a $7,500,000 non-refundable upfront cash payment, as well as payments for services provided. This upfront payment was amortized over the period of expected benefit.

On July 27, 2017, the Company received notice of termination from Alexion for the Company's LNP license agreement. The termination was driven by a strategic review of Alexion's business and research and development portfolio, which included a decision to discontinue development of mRNA therapeutics. The $7,500,000 upfront payment received in March 2017 is non-refundable, and the Company has recorded the upfront payment as well as any revenue and costs related to closeout procedures in the statement of operations and comprehensive loss for the period ended December 31, 2017.

(b) License agreement with Gritstone

On October 16, 2017, the Company entered into a license agreement with Gritstone that entitles Gritstone to research, develop, manufacture and commercialize products with the Company’s LNP technology. The Company received an upfront payment in November 2017, and is eligible to receive future potential payments including research services, development and commercial milestone payments and royalty payments on future product sales.

The Company determined the deliverables under the Agreements included the rights and license granted, involvement in the joint steering committee, and other services provided, as determined under the research plan. The license and involvement in the joint steering committee have been determined by the Company to not have standalone value. Therefore, these deliverables are treated as one unit of accounting and recognized as revenue over the performance period as the Company transfers the technical "know-how" for the customized formulations.

The Company has determined that other materials and services provided have standalone value. The relative fair values are estimated upon the execution of each activity and charged at rates comparable to market with embedded margins on each service activity.

The Company has not recorded any development and commercial milestone payments, as achievements of these were not probable as at December 31, 2017. As such, the accounting treatment for development and commercial milestone payments, as well as royalty payments on future product sales will be accounted for under the Company's application of the new revenue standard, ASC 606 - Revenue from Contracts with Customers, effective January 1, 2018 (see note 2).

On November 16, 2014, the Company signed a License Agreement and a Development and Supply Agreement (together, the “Agreements”) with Dicerna related to development, manufacture, and commercialization of products directed to the treatment of PH1. In consideration for the rights granted under the Agreements, Dicerna paid the Company an upfront cash payment of $2,500,000, as well as payments for manufacturing and services provided.

In September 2016, Dicerna announced the discontinuation of their DCR-PH1 program using the Company's technology. As such, the Company revised the completion date of performance period from March 2017 to September 30, 2016, at which time the Company had no further remaining performance obligations. This resulted in the recognition of $1,066,000 in Dicerna license fee revenue for the year ended December 31, 2016 and no revenue thereafter.

(d) Option and Services Agreements with Monsanto

On January 13, 2014, the Company and Monsanto signed an Option Agreement and a Services Agreement, which granted Monsanto an option to obtain a license to use the Company’s LNP delivery technology and related intellectual property for use in agriculture. Following the completion of the Phase A extension period in October 2015, no further research activities were conducted under the arrangement, as Monsanto did not elect to proceed to Phase B of the research plan. This resulted in the full release of Monsanto deferred revenue and a recognition of $13,384,000 in Monsanto revenue for the year ended December 31, 2015.

Under the Agreements, the Company has established a wholly-owned subsidiary, PADCo. The Company has determined that PADCo is a variable interest entity (“VIE”); however, Monsanto is the primary beneficiary of the arrangement. PADCo was established to perform research and development activities, which have been funded by Monsanto in return for a call option to acquire the equity or all of the assets of PADCo. On March 4, 2016, Monsanto exercised its option to acquire 100% of the outstanding shares of PADCo and paid the Company an option exercise fee of $1,000,000. From the acquisition of PADCo, Monsanto received a worldwide, exclusive right to use the Company’s proprietary delivery technology in the field of agriculture. The Company recorded the exercise fee received as a gain on disposition of a financial instrument in its consolidated statement of operations and comprehensive loss for the year ended December 31, 2016.

(e) Contract with United States Government’s Department of Defense (“DoD”) to develop TKM-Ebola

On July 14, 2010, the Company signed a contract with the DoD to advance TKM-Ebola, an RNAi therapeutic utilizing the Company’s lipid nanoparticle technology to treat Ebola virus infection.

Under the contract, the Company is reimbursed for costs incurred, including an allocation of overhead costs, and is paid an incentive fee. At the beginning of the fiscal year, the Company estimates its labor and overhead rates for the year ahead. At the end of the year the actual labor and overhead rates are calculated and revenue is adjusted accordingly. The Company’s actual labor and overhead rates will differ from its estimated rates based on actual costs incurred and the proportion of the Company’s efforts on contracts and internal products versus indirect activities. Within minimum and maximum collars, the amount of incentive fee the Company can earn under the contract varies based on costs incurred versus budgeted costs. During the contractual period, incentive fee revenue and total costs are impacted by management’s estimate and judgments which are continuously reviewed and adjusted as necessary using the cumulative catch-up method. For the years ended December 31, 2015 and 2016, the Company believes it can reliably estimate the final contract costs so has recognized the portion of expected incentive fee which has been earned to date.

On October 1, 2015, the Company received formal notification from the DoD that, due to the unclear development path for TKM-Ebola and TKM-Ebola-Guinea, the Ebola-Guinea Manufacturing and the Ebola-Guinea IND submission statements of work had been terminated, subject to the completion of certain post-termination obligations. The TKM-Ebola portion of the contract was completed in November 2015. The Company is currently conducting contract close out procedures with the DoD.

(f) Agreements with Spectrum Pharmaceuticals, Inc. (“Spectrum”)

On May 6, 2006, the Company signed a number of agreements with Talon Therapeutics, Inc. (“Talon”, formerly Hana Biosciences, Inc.) including the grant of worldwide licenses (the “Talon License Agreement”) for three of the Company’s chemotherapy products, Marqibo®, Alocrest ™ (Optisomal Vinorelbine) and Brakiva ™ (Optisomal Topotecan).

On August 9, 2012, the Company announced that Talon had received accelerated approval for Marqibo from the FDA for the treatment of adult patients with Philadelphia chromosome negative acute lymphoblastic leukemia in second or greater relapse or whose disease has progressed following two or more anti-leukemia therapies. Marqibo is a liposomal formulation of the chemotherapy drug vincristine. In the year ended December 31, 2012, the Company received a milestone of $1,000,000 based on the FDA’s approval of Marqibo and will receive royalty payments based on Marqibo’s commercial sales. There are no further milestones related to Marqibo but the Company is eligible to receive total milestone payments of up to $18,000,000 on Alocrest and Brakiva.

Talon was acquired by Spectrum in July 2013. The acquisition did not affect the terms of the license between Talon and the Company. On September 3, 2013, Spectrum announced that they had shipped the first commercial orders of Marqibo. In the year ended December 31, 2017, the Company recorded $191,000 in Marqibo royalty revenue (2016 - $212,000, 2015 -$240,000). In the year ended December 31, 2017, the Company accrued $5,000 in royalties due to TPC in respect of the Marqibo royalty earned by the Company (see note 10, contingencies and commitments).

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and equipment



December 31, 2017	Cost		Accumulated depreciation			Net book value
Lab equipment	$	9,567	$	(5,325	)	$	4,242
Leasehold improvements	12,578		(5,139		)	7,439
Computer hardware and software	2,318		(1,878		)	440
Furniture and fixtures	391		(329		)	62
Assets under construction	$	—				$	—
	$	24,854	$	(12,671	)	$	12,183



December 31, 2016	Cost		Accumulated depreciation			Net book value
Lab equipment	$	7,894	$	(4,305	)	$	3,589
Leasehold improvements	4,928		(4,454		)	474
Computer hardware and software	2,103		(1,665		)	438
Furniture and fixtures	374		(314		)	60
Assets under construction	$	2,384	$	—		$	2,384
	$	17,683	$	(10,738	)	$	6,945

As at December 31, 2017, all of the Company’s property and equipment is currently in use and no impairment has been recorded.

Share Capital

12 Months Ended

Dec. 31, 2017

Stockholders' Equity Note [Abstract]

Share capital

(a) Financing

On March 25, 2015, the Company announced that it had completed an underwritten public offering of 7,500,000 common shares, at a price of $20.25 per share, representing gross proceeds of $151,875,000. The Company also granted the underwriters a 30-day option to purchase an additional 1,125,000 shares for an additional $22,781,000 to cover any over-allotments. The underwriters did not exercise the option. The cost of financing, including commissions and professional fees, was $9,700,000, resulting in net proceeds of $142,177,000.

(b) Authorized share capital

The Company’s authorized share capital consists of an unlimited number of common and 1,164,000 preferred shares without par value.

On October 2, 2017, the Company announced that it entered into a subscription agreement with Roivant for the sale of Preferred Shares to Roivant for gross proceeds of $116,400,000. The Preferred Shares are non-voting and are convertible into common shares at a conversion price of $7.13 per share (which represents a 15% premium to the closing price of $6.20 per share). The purchase price for the Preferred Shares plus an amount equal to 8.75% per annum, compounded annually, will be subject to mandatory conversion into common shares on October 18, 2021 (subject to limited exceptions in the event of certain fundamental corporate transactions relating to Arbutus’ capital structure or assets, which would permit earlier conversion at Roivant’s option). After conversion of the Preferred Shares into common shares, based on the number of common shares outstanding on October 2, 2017, Roivant would hold 49.90% of the Company's common shares. Roivant has agreed to a four year lock-up period for this investment and its existing holdings in Arbutus. Roivant has also agreed to a four year standstill whereby Roivant will not acquire greater than 49.99% of the Company's common shares or securities convertible into common shares.

The initial investment of $50,000,000 closed on October 16, 2017, and the remaining amount of $66,400,000 closed on January 12, 2018 following regulatory and shareholder approvals, as applicable, under Canadian securities law.

The Company records the Preferred Shares wholly as equity under ASC 480, with no bifurcation of conversion feature from the host contract, given that the Preferred Shares cannot be cash settled and the redemption features are within the Company's control, which include a fixed conversion ratio with predetermined timing and proceeds. The Company accrues for the 8.75% per annum compounding coupon at each reporting period end date as an increase to share capital, and an increase to deficit (see statement of stockholder's equity).

(d) Warrants to purchase common shares

During the year ended December 31, 2017, there were 179,000 warrants exercised for $353,000 in cash (December 31, 2016 – 170,500 warrants for $445,000) and no warrants were exercised using the cashless exercise provision (December 31, 2016 – 0 warrants for 0 common shares). In March 2017, the remaining balance of 22,000 of the Company's warrants expired. The decrease in fair value from the previous balance sheet date relating to the expired warrants has been included in the total decrease in fair value of warrant liability in the Company's statement of comprehensive loss for the year ended December 31, 2017.

The following table summarizes the Company’s warrant activity for the years ended December 31, 2017 and 2016:



	Common shares purchasable upon exercise of warrants		Weighted average exercise price		Range of exercise prices					Weighted average remaining contractual life (years)	Aggregate intrinsic value
Balance, December 31, 2015	379,500		$	2.13	$2.03		—	$	2.62	0.8	$	879
Exercised	(170,500	)	2.53		2.53		—	2.53
Expired	(8,000	)	2.53		2.53		—	2.53
Balance, December 31, 2016	201,000		$	1.94	$	1.94	—	$	1.94	0.2	$	104
Exercised	(179,000	)	2.00		$	2.00	—	$	2.00
Expired	(22,000	)	2.00		$	2.00	—	$	2.00
Balance, December 31, 2017	—		—		—		—	—		—	$	—

The aggregate intrinsic value in the table above is calculated based on the difference between the exercise price of the warrants and the quoted price of the Company’s common stock as of the reporting date.

(e) Stock-based compensation

The Company has seven share-based compensation plans; the “2007 Plan”, the “2011 Plan”, the "2016 Plan", two “Designated Plans” (together, the “Arbutus Plans”), the “Protiva Option Plan”, and the "OnCore Option Plan".

On June 22, 2011, the shareholders of the Company approved an omnibus stock-based compensation plan (the “2011 Plan”). The Company’s pre-existing 2007 Plan was limited to the granting of stock options as equity incentive awards whereas the 2011 Plan also allows for the issuance of tandem stock appreciation rights, restricted stock units and deferred stock units (collectively, and including options, referred to as “Awards”). The 2011 Plan replaced the 2007 Plan. The 2007 Plan continued to govern the options granted thereunder. No further options were granted under the Company’s 2007 Plan.

Under the Company’s 2007 Plan the Board of Directors granted options to employees, directors and consultants of the Company. The exercise price of the options was determined by the Company’s Board of Directors but was always at least equal to the closing market price of the common shares on the day preceding the date of grant and the term of options granted did not exceed 10 years. The options granted generally vested over three years for employees and immediately for directors.

Under the Company’s 2011 Plan the Board of Directors may grant options, and other types of Awards, to employees, directors and consultants of the Company. The exercise price of the options is determined by the Company’s Board of Directors but will be at least equal to the closing market price of the common shares on the day preceding the date of grant and the term may not exceed 10 years. Options granted generally vest over three years for employees and immediately for directors.

At the Company’s annual general and special meeting of shareholders on May 8, 2014 and July 9, 2015, the shareholders of the Company approved respectively, a 800,000 and a 3,500,000 increase in the number of stock-based compensation awards that the Company is permitted to issue under the 2011 Plan.

At the Company’s annual general and special meeting of shareholders on May 19, 2016, the shareholders of the Company approved the adoption of the Company's 2016 Omnibus Share and Incentive Plan (the "2016 Plan") and the reserve of 5,000,000 shares of the Company issuable pursuant to awards under the 2016 Plan. These include both equity-classified and liability-classified stock options. The Company's 2011 Omnibus Share Compensation Plan, as amended, also remains in effect.

Additionally, the Company granted a total of 200,000 options in 2013 to two executive officers in conjunction with their new appointments as executive officers. These options were granted in accordance with the policies of the Toronto Stock Exchange and pursuant to newly designated share compensation plans (the “Designated Plans”). During 2016, one of the two executive officers departed from the Company, and the unexercised options under his Designated Plan expired. No new options can be granted under the Designated Plans, resulting in one Designated Plan remaining at the end of 2017. The Designated Plan is governed by substantially the same terms as the 2011 Plan. Hereafter, information on options governed by the 2007 Plan, the 2011 Plan, the 2016 Plan and the Designated Plan (the "Arbutus Plans") is presented on a consolidated basis as the terms of the five plans are similar. Information on the Protiva Option Plan and the OnCore Option Plan are presented separately.

Stock option activity for the Arbutus Plans

Equity-classified stock option activity:



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value
Balance, December 31, 2014	1,530,138		6.29		15,004
Options granted	1,309,625		16.57
Options exercised	(398,293	)	3.93		5,386
Options forfeited, canceled or expired	(151,207	)	15.09
Balance, December 31, 2015	2,290,263		11.22		994
Options reclassified to liability¹	(718,333	)	5.23		604
Options granted	1,789,599		3.89
Options exercised	(56,125	)	2.18		121
Options forfeited, canceled or expired	(394,200	)	10.18
Balance, December 31, 2016	2,911,204		$	8.53	$	56
Options granted	2,026,500		$	3.20
Options exercised	(11,105	)	$	3.45	$	13
Options forfeited, canceled or expired	(208,272	)	$	11.41
Balance, December 31, 2017	4,718,327		$	6.06	$	5,842


1.	Due to the change in the Company's functional currency as of January 1, 2016, certain stock option awards with exercise prices denominated in Canadian dollars changed from equity classification to liability classification - see note 2.

Options under the Arbutus Plans expire at various dates from March 31, 2018 to November 7, 2027.

The following table summarizes information pertaining to stock options outstanding at December 31, 2017 under the Arbutus Plans:



			Options outstanding December 31, 2017				Options exercisable December 31, 2017
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price (US$)		Number of options exercisable	Weighted average exercise price (US$)
$1.19	to	$3.11	114,887	5.5	2.33		83,887	2.10
$3.12	to	$3.22	1,807,000	9.2	3.15		—	N/A
$3.23	to	$3.92	368,763	8.8	3.58		186,096	3.57
$3.93	to	$3.95	1,313,682	8.2	3.94		432,365	3.94
$3.96	to	$14.32	479,537	7.0	10.48		382,701	9.97
$14.33	to	$16.16	5,500	6.6	14.74		5,500	14.74
$16.17	to	$17.57	628,958	7.2	17.57		429,582	17.57
$1.19	to	$17.57	4,718,327	8.3	$	6.06	1,520,131	$	9.20

At December 31, 2017, there were 1,520,131 options exercisable (December 31, 2016 - 699,241; December 31, 2015 – 938,730). The weighted average remaining contractual life of exercisable options as at December 31, 2017 was 7.4 years.

The aggregate intrinsic value of in-the-money options exercisable at December 31, 2017 was $1,098,000.

A summary of the Company’s non-vested stock option activity and related information for the year ended December 31, 2017 is as follows:



	Number of optioned common shares		Weighted average fair value
Non-vested at December 31, 2016	2,211,963		$	5.34
Options granted	2,026,500		2.15
Options vested	(972,723	)	5.82
Non-vested options forfeited	(67,544	)	4.73
Non-vested at December 31, 2017	3,198,196		$	3.23

The weighted average remaining contractual life for options expected to vest at December 31, 2017 was 8.3 years and the weighted average exercise price for these options was $6.06 per share.

The aggregate intrinsic value of options expected to vest as at December 31, 2017 was $5,842,000 (December 31, 2016 - $0; December 31, 2015 -$10,000).

The total fair value of options that vested during the year ended December 31, 2017 was $5,657,000 (December 31, 2016 - $5,058,000; December 31, 2015 -$1,718,000).

Valuation assumptions for the Arbutus Plans

On March 3, 2015, the Company voluntarily de-listed from the Toronto Stock Exchange. All stock options granted after March 3, 2015 were denominated in US dollars based on the Company's stock price on the NASDAQ. The methodology and assumptions used to estimate the fair value of stock options at date of grant under the Black-Scholes option-pricing model remain unchanged. Assumptions on the dividend yield are based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends. Assumptions about the Company’s expected stock-price volatility are based on the historical volatility of the Company’s publicly traded stock. The risk-free interest rate used for each grant is equal to the zero coupon rate for instruments with a similar expected life. Expected life assumptions are based on the Company’s historical data. The Company recognizes forfeitures as they occur, and the effects of forfeitures are reflected in stock-based compensation expense recorded in the statement of operations and comprehensive loss for the year ended December 31, 2017. The weighted average option pricing assumptions for options granted during the year are as follows:



	Year ended December 31
	2017		2016		2015
Dividend yield	—	%	—	%	—	%
Expected volatility	73.05	%	77.99	%	76.88	%
Risk-free interest rate	1.28	%	0.90	%	1.10	%
Expected average option term	6.9 years		7.3 years		7.5 years

Liability-classified stock option activity:

Valuation assumptions

Liability options are re-measured to their fair values at each reporting date, using the Black-Scholes valuation model. The methodology and assumptions prevailing at the re-measurement date used to estimate the fair values of liability options remain unchanged from the date of grant of equity classified stock option awards. Assumptions about the Company’s expected stock-price volatility are based on the historical volatility of the Company’s publicly traded stock. The risk-free interest rate used for each grant is equal to the zero coupon rate for instruments with a similar expected life. Expected life assumptions are based on the Company’s historical data. The weighted average Black-Scholes option-pricing assumptions and the resultant fair values as at December 31, 2016 and December 31, 2017, are presented in the following table:



	December 31,			December 31,
	2017			2016
Dividend yield	—		%	—		%
Expected volatility	70.31		%	66.18		%
Risk-free interest rate	2.10		%	0.88		%
Expected average term (years)	4.3			3.6
Fair value of options outstanding	$	2.75		$	0.87
Fair value of vested liability-classified options (in thousands)	$	1,239		$	553

Stock option activity for liability options



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value
Balance, December 31, 2016	638,500		$	5.48	$	116
Options exercised	(25,000	)	2.37		103
Options forfeited, canceled, or expired	(162,000	)	6.54		—
Balance, December 31, 2017	451,500		$	5.78	$	525

Liability options expire at various dates from March 31, 2018 to May 7, 2024.

The following table summarizes information pertaining to liability options outstanding at December 31, 2017:



			Options outstanding December 31, 2017				Options exercisable December 31, 2017
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price		Number of options exercisable	Weighted average exercise price
$1.35	to	$1.67	65,000	2.8	$	1.38	65,000	$	1.38
$1.68	to	$3.38	75,000	2.9	2.45		75,000	2.45
$3.39	to	$4.27	75,000	3.2	3.94		75,000	3.94
$4.28	to	$5.85	14,000	0.3	4.45		14,000	4.45
$5.86	to	$8.61	150,000	5.8	7.25		150,000	7.25
$8.62	to	$13.04	72,500	6.2	12.30		72,500	12.30
$1.35	to	$13.04	451,500	4.3	$	5.78	451,500	$	5.78

During the year-ended December 31, 2017, 14,750 options vested with a weighted average exercise price of $12.83 and a total fair value of $36,100. As at December 31, 2017, all liability options were vested.

Protiva Option Plan

On May 30, 2008, as a condition of the acquisition of Protiva Biotherapeutics Inc., a total of 350,457 common shares of the Company were reserved for the exercise of 519,073 Protiva share options (“Protiva Options”). The Protiva Options have an exercise price of C$0.30, were fully vested and exercisable as of May 30, 2008. As at December 31, 2017, the outstanding options expire on March 1, 2018 and upon exercise each option will be converted into approximately 0.6752 shares of the Company (the same ratio at which Protiva common shares were exchanged for Company common shares at completion of the acquisition of Protiva). The Protiva Options are not part of the Arbutus Plans and the Company is not permitted to grant any further Protiva Options.

The following table sets forth outstanding options under the Protiva Option Plan:



	Number of Protiva Options		Equivalent number of Company common shares		Weighted average exercise price (C$)		Weighted average exercise price (US$)
Balance, December 31, 2014	433,740		292,845		$	0.30	0.27
Options exercised	(358,675	)	(242,164	)	0.30		0.23
Options forfeited, canceled or expired	(8,065	)	(5,445	)	0.30		0.23
Balance, December 31, 2015	67,000		45,236		0.30		0.22
Options exercised	(21,000	)	(14,178	)	0.30		0.23
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2016	46,000		31,058		0.30		0.22
Options exercised	(6,000	)	(4,051	)	0.30		0.23
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2017	40,000		27,007		$	0.30	$	0.24

The weighted average remaining contractual life of exercisable Protiva Options as at December 31, 2017 was 0.2 years.

The aggregate intrinsic value of Protiva Options outstanding at December 31, 2017 was $127,000. The intrinsic value of Protiva Options exercised in the year ended December 31, 2017 was $10,000 (2016 - $49,000; 2015 -$1,249,000).

OnCore Option Plan

As at the acquisition date in March 2015, the Company reserved 184,332 shares for the future exercise of OnCore (Arbutus Inc.) stock options. The total fair value of OnCore stock options at the date of acquisition has been determined to be $3,287,000, using the Black-Scholes pricing model with an assumed risk-free interest rate of 0.97%, volatility of 78%, a zero dividend yield and an expected life of 8 years, which are consistent with the assumption inputs used by the Company to determine the fair value of its options. Of the total fair value, $1,127,000 has been attributed as pre-combination service and included as part of the total acquisition consideration. The post-combination attribution of $2,160,000 will be recognized as compensation expense over the vesting period of the stock options through to December 2018.

Following the merger, the Company is not permitted to grant any further options under the OnCore Option Plan. The Company has included $576,000 of compensation expense related to the vesting of Arbutus Inc. stock options for the year ended December 31, 2017.

The following table sets forth outstanding options under the OnCore Option Plan:



	Number of OnCore Options	Equivalent number of Company common shares	Weighted average exercise price (US$)
Balance, December 31, 2016	183,040	184,332	$	0.57
Options exercised	—	—	N/A
Options forfeited, canceled or expired	—	—	N/A
Balance, December 31, 2017	183,040	184,332	$	0.57

At December 31, 2017, there were 150,913 OnCore options (151,978 Arbutus equivalent) exercisable with a weighted average exercise price of $0.56. The weighted average remaining contractual life of exercisable options as at December 31, 2017 was 6.9 years. The aggregate intrinsic value of in-the-money options exercisable at December 31, 2017 was $682,000.

A summary of the OnCore Option Plan's non-vested stock option activity and related information for the year ended December 31, 2017 is as follows:



	Number of OnCore Options		Equivalent number of Company common shares		Weighted average fair value (US$)
Non-vested at December 31, 2016	63,051		63,497		$	16.80
Options vested	(30,923	)	(31,143	)	16.17
Non-vested options forfeited	—		—		N/A
Non-vested at December 31, 2017	32,128		32,354		$	16.18

The weighted average remaining contractual life for options expected to vest at December 31, 2017 was 6.9 years and the weighted average exercise price for these options was $0.57 per share.

The aggregate intrinsic value of options expected to vest as at December 31, 2017 was $144,000.

The total fair value of options that vested during the year ended December 31, 2017 was $611,000.

Stock-based compensation expense

Total stock-based compensation expense is comprised of: (1) the vesting options awarded to employees under the Arbutus and OnCore option plans calculated in accordance with the fair value method as described above; and (2) the expiration of repurchase rights related to the post-combination service portion of the total fair value of shares issued to Arbutus Inc.'s employees.

The total stock-based compensation has been recorded in the consolidated statement of operations and comprehensive income (loss) as follows:



	Year ended December 31
	2017		2016		2015
Research, development, collaborations and contracts expenses	$	9,236	$	11,155	$	7,868
General and administrative expenses	5,881		28,004		14,225
Total	$	15,117	$	39,159	$	22,093

At December 31, 2017, there remains $5,747,000 of unearned compensation expense related to unvested equity employee stock options to be recognized as expense over a weighted-average period of approximately 20 months.

Awards outstanding and available for issuance

Combining all of the Company’s share-based compensation plans, at December 31, 2017, the Company has 5,381,163 options outstanding and a further 5,084,189 Awards available for issuance.

(f) Replacement awards

Included in the total consideration transferred for the acquisition of Arbutus Inc. in March 2015 are common shares issued as replacement awards, which are subject to repurchase provisions. The total fair value of these common shares attributed to the post acquisition period was approximately $56,934,000 and is being recognized as compensation expense over the expiry period of repurchase provision rights subsequent to the acquisition date.

For the year-ended December 31, 2017, all remaining repurchase provision rights expired and the Company recorded compensation expense $7,972,000 (2016 - $31,986,000; 2015 - $16,687,000) in stock-based compensation.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section S99
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income taxes

Income tax (recovery) expense varies from the amounts that would be computed by applying the combined Canadian federal and provincial income tax rate of 26% (2015 - 26%; 2014 – 26%) to the loss before income taxes as shown in the following tables:



	Year ended December 31,
	2017			2016			2015
Computed taxes (recoveries) at Canadian federal and provincial tax rates	$	(28,270	)	$	(127,183	)	$	(20,100	)
Difference due to change in tax rate on opening deferred taxes	(6,633		)	—			—
Permanent and other differences	1,476			(3,598		)	769
Change in valuation allowance - other	6,945			17,043			3,675
Difference due to income taxed at foreign rates	(966		)	(47,962		)	(7,874		)
Stock-based compensation	3,128			9,727			7,345
Impairment of goodwill	—			46,971			—
Deferred income tax recovery	$	(24,320	)	$	(105,002	)	$	(16,185	)

Effective November 2, 2017, the British Columbia provincial corporate tax rate increased from 11% to 12%, starting January 1, 2018. The overall increase in tax rates in 2018 will result in an increase in the Company's statutory tax rate from 26% in 2017 to 27% in 2018 and onward.

On December 22, 2017, the Tax Cuts and Jobs Act (the “2017 Tax Act”) was signed into law making significant changes to the Internal Revenue Code. Changes include, but are not limited to, a federal corporate tax rate decrease from 35% to 21% for tax years beginning after December 31, 2017. Certain income tax effects of the 2017 Tax Act, principally due to the write-down of our net deferred tax assets, are reflected in our financial results in accordance with Staff Accounting Bulletin No. 118 (SAB 118), which provides SEC staff guidance regarding the application of Accounting Standards Codification (ASC) Topic 740, Income Taxes, in the reporting period in which the 2017 Tax Act became law. At December 31, 2017, we have not completed our accounting for the tax effects of enactment of the Act; however, we have made a reasonable estimate of the effects on our existing deferred tax balances. We have remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. However, we are still analyzing certain aspects of the Act and refining our calculations, which could potentially affect the measurement of these balances or potentially give rise to new deferred tax amounts. The provisional amount recorded related to the re-measurement of our deferred tax assets was a reduction of $13.4 million to deferred tax liabilities and a reduction of $3.5 million to our deferred tax assets, which have a full valuation allowance provided against them.

On November 23, 2011, the Company was registered as a corporation under the Business Activity Act in the province of British Columbia. Under this program, provincial corporation tax charged on foreign income earned from the Company’s patents will be eligible for a 75% tax refund up to a maximum of C$8,000,000. This program was eliminated on October 23, 2017.

As at December 31, 2017, the Company has investment tax credits available to reduce Canadian federal income taxes of $9,546,000 (December 31, 2016 - $10,245,000) and provincial income taxes of $4,866,000 (December 31, 2016 - $5,337,000), expiring between 2027 and 2037. In addition, the Company has research and development credits of $3,639,000 (December 31, 2016 - $1,454,000) available for indefinite carry-forward, which can be used to reduce future taxable income in the U.S.

At December 31, 2017, the Company has scientific research and experimental development expenditures of $61,493,000 (December 31, 2016 - $65,332,000) available for indefinite carry-forward and $124,451,000 (December 31, 2016 - $71,460,000) of net operating losses due to expire between 2027 and 2037 and which can be used to offset future taxable income in Canada.

As at December 31, 2017, the Company has $13,723,000 (December 31, 2016 - $14,621,000) of net operating losses due to expire between 2030 and 2037, which can be used to offset future taxable income in the U.S. Future use of a portion of the U.S. loss carry-forwards is subject to limitations under the Internal Revenue Code Section 382.

As a result of ownership changes occurring on October 1, 2014 and March 4, 2015, the Company's ability to use these losses may be limited. Losses incurred to date may be further limited if a subsequent change in control occurs.

Significant components of the Company’s deferred tax assets and liabilities are shown below:



	As at December 31,
	2017			2016
Deferred tax assets (liabilities):
Non-capital loss carryforwards	$	36,652		$	24,275
Research and development deductions	16,603			16,986
Book amortization in excess of tax	(650		)	451
Share issue costs	456			486
Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes	1,162			410
Tax value in excess of accounting value in lease inducements	173			58
Federal investment tax credits	9,079			8,630
Provincial investment tax credits	4,819			5,270
In-process research and development	(16,943		)	(41,263		)
Upfront license fees	311			536
Other	2,017			1,435
Total deferred tax assets (liabilities)	53,679			17,274
Valuation allowance	(70,622		)	(58,537		)
Net deferred tax assets (liabilities)	$	(16,943	)	$	(41,263	)

Loan Payable	12 Months Ended
Loan Payable	Dec. 31, 2017
Debt Disclosure [Abstract]
Loan Payable	Loan payable On December 27, 2016, the Company obtained a loan of $12,001,000 from Wells Fargo in the form of a promissory note for the purpose of financing its operations, including the expansion of laboratory facilities for its U.S. operations. The loan accrues interest daily based on an interest rate with a variable and fixed component. The variable component is the one-month London Interbank Offered Rate (LIBOR), and the fixed component is a margin of 1.25% per annum. The carrying value of the loan is recorded at the principal plus any accrued interest not yet paid. The loan is due on December 27, 2019. The loan is secured by the Company's cash of $12,601,000, and is restricted from use until the loan has been settled in full. The Company invested the restricted cash in a two-year fixed certificate of deposit with Wells Fargo (see note 2) and is presented as restricted investment in the Company's balance sheet for the period ended December 31, 2017.

Contingencies and Commitments

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Contingencies and commitments

Property lease

The total minimum rent and estimated operating cost commitment, net of lease inducements, for both our head office in Burnaby and Warminster facility is as follows:



Year ended December 31, 2018	$	1,607
Year ended December 31, 2019	1,243
Year ended December 31, 2020	656
Year ended December 31, 2021	673
Year ended December 31, 2022 and after	3,813
	$	7,992

The Company’s lease expense, for the year ended December 31, 2017 of $1,653,000 has been recorded in the consolidated statements of operations and comprehensive loss (2016 of $1,341,000; 2015 of $1,158,000).

Product development partnership with the Canadian Government

The Company entered into a Technology Partnerships Canada (TPC) agreement with the Canadian Federal Government on November 12, 1999. Under this agreement, TPC agreed to fund 27% of the costs incurred by the Company, prior to March 31, 2004, in the development of certain oligonucleotide product candidates up to a maximum contribution from TPC of $7,179,000 (C$9,330,000). As at December 31, 2017, a cumulative contribution of $2,951,000 (C$3,702,000) had been received and the Company does not expect any further funding under this agreement. In return for the funding provided by TPC, the Company agreed to pay royalties on the share of future licensing and product revenue, if any, that is received by the Company on certain non-siRNA oligonucleotide product candidates covered by the funding under the agreement. These royalties are payable until a certain cumulative payment amount is achieved or until a pre-specified date. In addition, until a cumulative amount equal to the funding actually received under the agreement has been paid to TPC, the Company agreed to pay 2.5% royalties on any royalties the Company receives for Marqibo. For the year ended December 31, 2017, the Company earned royalties on Marqibo sales in the amount of $191,000 (see note 4(f)), resulting in $5,000 recorded by the Company as royalty payable to TPC (2016 - $5,000; 2015 -$6,000). The cumulative amount paid or accrued up to December 31, 2017 was $22,000, resulting in the contingent amount due to TPC being $2,929,000 (C$3,674,000).

Arbitration with the University of British Columbia (“UBC”)

Certain early work on lipid nanoparticle delivery systems and related inventions was undertaken at UBC. These inventions are licensed to the Company by UBC under a license agreement, initially entered in 1998 as amended in 2001, 2006 and 2007. The Company has granted sublicenses under the UBC license to Alnylam. Alnylam has in turn sublicensed back to the Company under the licensed UBC patents for discovery, development and commercialization of siRNA products. Certain sublicenses to other parties were also granted.

On November 10, 2014, UBC filed a demand for arbitration against the Company and on January 16, 2015, filed a Statement of Claim, which alleges entitlement to $3,500,000 in allegedly unpaid royalties based on publicly available information, and an unspecified amount based on non-public information. UBC also seeks interest and costs, including legal fees. The Company filed its Statement of Defense to UBC's Statement of Claims, as well as filed a Counterclaim involving a patent application that the Company alleges UBC wrongly licensed to a third party rather than to the Company. The Company seeks license payments for said application, and an exclusive worldwide license to said application. The proceeding has been divided into three phases, with a first hearing that took place in June 2017. The arbitrator determined in the first phase which agreements are sublicense agreements within UBC's claim, and which are not. No finding was made as to whether any licensing fees are due to UBC under these agreements; this will be the subject of the second phase of arbitration. The arbitrator also held that the patent application that is the subject of the Counterclaim was not required to be licensed to Arbutus. A schedule for the remaining phases has not yet been set. Arbitration and related matters are costly and may divert the attention of the Company's management and other resources that would otherwise be engaged in other activities. However, the Company notes that arbitration is subject to inherent uncertainty and an arbitrator could rule against the Company. The Company has not recorded an estimate of the possible loss associated with this arbitration, due to the uncertainties related to both the likelihood and amount of any possible loss or range of loss. Costs related to the arbitration have been recorded in the statement of operations and comprehensive loss by the Company as incurred.

Litigation with Acuitas Therapeutics (“Acuitas”)

In August 2017, the Company provided Acuitas with notice that it considered Acuitas to be in material breach of the cross-license agreement. The cross-license agreement provides that it may be terminated upon any material breach by the other party 60 days after receipt of written notice of termination describing the material breach in reasonable detail. In October 2016, Acuitas filed a Notice of Civil Claim in the Supreme Court of British Columbia seeking an order that the Company perform its obligations under the Cross License Agreement, for damages ancillary to specific performance, injunctive relief, interest and costs. The Company disputed Acuitas’ position, and filed a Counterclaim seeking a declaration that Acuitas is in breach of the Cross License Agreement, and claiming injunctive relief, damages, interest and costs.

In January 2017, the Company filed an application seeking an order to enjoin Acuitas from, among other things, entering into any further agreements purporting to sublicense Arbutus’ technology from the date of the order to the date of trial or further order from the Court. In February 2017, the Company announced that the Supreme Court of British Columbia granted its request for a pre-trial injunction against Acuitas, preventing Acuitas from further sublicensing of the Company's lipid nanoparticle (LNP) technology until the end of October, or further order of the Court. Under the terms of the pre-trial injunction, Acuitas is prevented from entering into any new agreements which include sublicensing of the Company's LNP. In March 2017, Acuitas sought leave to appeal from the injunction decision and in April 2017, the appeal was denied. In September 2017, the injunction order was extended by consent to March 2, 2018. In February 2018, the contractual issues concerning the cross-license agreement (excluding the claims for damages) were settled out of court, resulting in the termination of Acuitas’ rights to further use or sublicense our LNP technology, making permanent the effect of the Court’s prior injunction.

Arbitration and related matters are costly and may divert the attention of the Company’s management and other resources that would otherwise be engaged in other activities. Costs related to the arbitration are recorded by the Company as incurred. No contingent asset was recorded by the Company for the period ended December 31, 2017, as the settlement occurred in February 2018, and the terms were determined after December 31.

Contingent consideration from Arbutus Inc. acquisition of Enantigen and License Agreements between Enantigen and Baruch S. Blumberg Institute (Blumberg) and Drexel

In October 2014, Arbutus Inc. acquired all of the outstanding shares of Enantigen pursuant to a stock purchase agreement. Through this transaction, Arbutus Inc. acquired a HBV surface antigen secretion inhibitor program and a capsid assembly inhibitor program, each of which are now assets of Arbutus, following the Company’s merger with Arbutus Inc.

Under the stock purchase agreement, Arbutus Inc. agreed to pay up to a total of $21,000,000 to Enantigen’s selling stockholders upon the achievement of certain triggering events related to HBV therapies. The first triggering event is enrollment of the first patient in a Phase 1b clinical trial in HBV patients, which the Company believes is likely to occur in the next twelve-month period.

The regulatory, development and sales milestone payments had an estimated fair value of approximately $6,727,000 as at the date of acquisition of Arbutus Inc., and were treated as contingent consideration payable in the purchase price allocation. The contingent consideration was calculated based on information available at the date of acquisition, using a probability weighted assessment of the likelihood the milestones would be met and the estimated timing of such payments, and then the potential contingent payments were discounted to their present value using a probability adjusted discount rate that reflects the early stage nature of the development program, time to complete the program development, and market comparatives.

Contingent consideration is a financial liability and measured at its fair value at each reporting period, with any changes in fair value from the previous reporting period recorded in the statement of operations and comprehensive loss (see note 2).

Drexel and Blumberg

In February 2014, Arbutus Inc. entered into a license agreement with Blumberg and Drexel that granted an exclusive, worldwide, sub-licensable license to three different compound series: cccDNA inhibitors, capsid assembly inhibitors and HCC inhibitors.

In partial consideration for this license, Arbutus Inc. paid a license initiation fee of $150,000 and issued warrants to Blumberg and Drexel. The warrants were exercised in 2014. Under this license agreement, Arbutus Inc. also agreed to pay up to $3,500,000 in development and regulatory milestones per licensed compound series, up to $92,500,000 in sales performance milestones per licensed product, and royalties in the mid-single digits based upon the proportionate net sales of licensed products in any commercialized combination. The Company is obligated to pay Blumberg and Drexel a double digit percentage of all amounts received from the sub-licensees, subject to customary exclusions.

In November 2014, Arbutus Inc. entered into an additional license agreement with Blumberg and Drexel pursuant to which it received an exclusive, worldwide, sub-licensable license under specified patents and know-how controlled by Blumberg and Drexel covering epigenetic modifiers of cccDNA and STING agonists. In consideration for these exclusive licenses, Arbutus Inc. made an upfront payment of $50,000. Under this agreement, the Company will be required to pay up to $1,000,000 for each licensed product upon the achievement of a specified regulatory milestone and a low single digit royalty, based upon the proportionate net sales of compounds covered by this intellectual property in any commercialized combination. The Company is also obligated to pay Blumberg and Drexel a double digit percentage of all amounts received from its sub-licensees, subject to exclusions.

Research Collaboration and Funding Agreement with Blumberg

In October 2014, Arbutus Inc. entered into a research collaboration and funding agreement with Blumberg under which the Company will provide $1,000,000 per year of research funding for three years, renewable at the Company’s option for an additional three years, for Blumberg to conduct research projects in HBV and liver cancer pursuant to a research plan to be agreed upon by the parties. Blumberg has exclusivity obligations to Arbutus with respect to HBV research funded under the agreement. In addition, the Company has the right to match any third party offer to fund HBV research that falls outside the scope of the research being funded under the agreement. Blumberg has granted the Company the right to obtain an exclusive, royalty bearing, worldwide license to any intellectual property generated by any funded research project. If the Company elects to exercise its right to obtain such a license, the Company will have a specified period of time to negotiate and enter into a mutually agreeable license agreement with Blumberg. This license agreement will include the following pre negotiated upfront, milestone and royalty payments: an upfront payment in the amount of $100,000; up to $8,100,000 upon the achievement of specified development and regulatory milestones; up to $92,500,000 upon the achievement of specified commercialization milestones; and royalties at a low single to mid-single digit rates based upon the proportionate net sales of licensed products from any commercialized combination.

On June 5, 2016, the Company and Blumberg entered into an amended and restated research collaboration and funding agreement, primarily to: (i) increase the annual funding amount to Blumberg from $1,000,000 to $1,100,000; (ii) extend the initial term through to October 29, 2018; (iii) provide an option for the Company to extend the term past October 29, 2018 for two additional one year terms; and (iv) expand the Company's exclusive license under the Agreement to include the sole and exclusive right to obtain an exclusive, royalty-bearing, worldwide and all-fields license under Blumberg's rights in certain other inventions described in the agreement.

Concentrations of Business Risk

12 Months Ended

Dec. 31, 2017

Risks and Uncertainties [Abstract]

Concentrations of business risk

Credit risk

Credit risk is defined by the Company as an unexpected loss in cash and earnings if a collaborative partner is unable to pay its obligations in due time. The Company’s main source of credit risk is related to its accounts receivable balance which principally represents temporary financing provided to collaborative partners in the normal course of operations.

The Company does not currently maintain a provision for bad debts as the majority of accounts receivable are from collaborative partners or government agencies and are considered low risk.

The carrying amount of financial assets represents the maximum credit exposure. The maximum exposure to credit risk at December 31, 2017 was the accounts receivable balance of $402,000 (2016 - $273,000).

All accounts receivable balances were current as at December 31, 2017 and December 31, 2016.

Significant collaborators and customers risk

We depend on a small number of collaborators and customers for a significant portion of our revenues (see note 4).

Liquidity Risk

Liquidity risk results from the Company’s potential inability to meet its financial liabilities, for example payments to suppliers. The Company ensures sufficient liquidity through the management of net working capital and cash balances.

The Company’s liquidity risk is primarily attributable to its cash and cash equivalents, and short-term investments. The Company limits exposure to liquidity risk on its liquid assets through maintaining its cash and cash equivalent, and short-term investments with high-credit quality financial institutions. Due to the nature of these investments, the funds are available on demand to provide optimal financial flexibility.

The Company believes that its current sources of liquidity are sufficient to cover its likely applicable short term cash obligations. The Company’s financial obligations include accounts payable and accrued liabilities which generally fall due within 45 days. The net liquidity of the Company is considered to be the cash and cash equivalents and short-term investments less accounts payable and accrued liabilities.



	December 31, 2017			December 31, 2016
Cash, cash equivalents and short-term investments	$	126,352		$	130,559
Less: Accounts payable and accrued liabilities	$	(10,646	)	$	(9,910	)
	$	115,706		$	120,649

Foreign currency risk

The results of the Company’s operations are subject to foreign currency transaction and translation risk as the Company’s revenues and expenses are denominated in both Canadian and US dollars. The fluctuation of the Canadian dollar in relation to the US dollar will consequently have an impact upon the Company’s reported income or loss and may also affect the value of the Company’s assets, liabilities, and the amount of shareholders’ equity both as recorded in the Company’s financial statements, in the US functional currency, and as reported, for presentation purposes, in the US dollar.

The Company manages its foreign currency risk by using cash received in a currency to pay for expenses in that same currency, whenever possible. The Company’s policy to maintain US and Canadian dollar cash and investment and short-term investment balances based on long term forecasts of currency needs thereby creating a natural currency hedge.

The Company has not entered into any agreements or purchased any instruments to hedge possible currency risks. The Company’s exposure to Canadian dollar currency expressed in US dollars was as follows:



(in US$)	December 31, 2017			December 31, 2016
Cash and cash equivalents and short-term investments	$	25,921		$	43,094
Accounts receivable	375			289
Accrued revenue	—			128
Accounts payable and accrued liabilities	(1,273		)	(3,238		)
	$	25,023		$	40,273

An analysis of the Company’s sensitivity to foreign currency exchange rate movements is not provided in these financial statements as the Company’s Canadian dollar cash holdings and expected Canadian dollar revenues are sufficient to cover Canadian dollar expenses for the foreseeable future.

Interim Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Interim financial data (unaudited)



	2017
	Q1			Q2			Q3			Q4			Total
Revenue	$	235		$	1,039		$	6,892		$	2,534		$	10,700
Loss from operations	(18,299		)	(19,485		)	(12,897		)	(60,249		)	(110,930		)
Net loss	$	(18,627	)	$	(18,255	)	$	(11,600	)	$	(35,931	)	$	(84,413	)
Basic and diluted net loss per common share	$	(0.34	)	$	(0.33	)	$	(0.21	)	$	(0.67	)	$	(1.56	)



	2016
	Q1			Q2			Q3			Q4			Total
Revenue	$	603		$	309		$	774		$	(195	)	$	1,491
Loss from operations	(19,977		)	(195,248		)	(18,975		)	(257,439		)	(491,639		)
Net loss	$	(15,874	)	$	(130,000	)	$	(19,595	)	$	(218,695	)	$	(384,164	)
Basic and diluted net loss per common share	$	(0.31	)	$	(2.47	)	$	(0.37	)	$	(4.05	)	$	(7.24	)

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent events	Subsequent events (a) Closing of Second Tier of a $116.4 million Strategic Investment from Roivant Sciences On January 12, 2018, the Company closed the Tier 2 issue and sale of 664,000 Series A participating convertible preferred shares to Roivant for gross proceeds of $66,400,000, following receipt of the approval of the Company's shareholders on January 11, 2018. The Tier 2 closing represents the second of two tiers of Preferred Shares issued to Roivant and, together with the previously announced Tier 1 closing in October 2017 (see note 6), comprise the previously announced $116,400,000 strategic investment by Roivant in the Company. (b) Consolidation of HBV business in Warminster, PA site On February 2, 2018, the Company announced a site consolidation and organizational structuring to better align its HBV business in Warminster, PA. To achieve this alignment, the Company will reduce its global workforce by approximately 31% and plans to close its Burnaby facility. The Company will incur restructuring costs related to one-time employee termination benefits, employee relocation costs, and site closure costs estimated to be $5,000,000, which will be primarily paid in cash in the second quarter of 2018. The Company and Roivant are currently negotiating a structure to jointly develop the Company's LNP and GalNAc technologies. (c) Settlement of Litigation, Terminating Acuitas’ Rights to LNP Technology In February 2018, the contractual issues concerning the cross-license agreement (excluding the claims for damages) were settled out of court, resulting in the termination of Acuitas’ rights to further use or sublicense our LNP technology, making permanent the effect of the Court’s prior injunction. Refer to note 10 - contingencies and commitments, and Item 3, "Legal Proceedings" in Part I of this annual report on Form 10-K for more information.

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Basis of presentation

Recast of Comparative Financial Statements

Foreign currency translation and functional currency conversion

Use of estimates

Cash and cash equivalents

Short-term investments

Loan payable and restricted investment

Fair value of financial instruments

We measure certain financial instruments and other items at fair value.


•	Level 1 inputs are quoted market prices for identical instruments available in active markets.


•	Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability either directly or indirectly. If the asset or liability has a contractual term, the input must be observable for substantially the full term. An example includes quoted market prices for similar assets or liabilities in active markets.


•	Level 3 inputs are unobservable inputs for the asset or liability and will reflect management’s assumptions about market assumptions that would be used to price the asset or liability.

Property and equipment



	Useful life (years)
Laboratory equipment		5
Computer and office equipment	2	—	5
Furniture and fixtures		5

Leasehold improvements are depreciated over their estimated useful lives but in no case longer than the lease term, except where lease renewal is reasonably assured.

Impairment of property and equipment

Goodwill and intangible assets

The costs incurred in establishing and maintaining patents for intellectual property developed internally are expensed in the period incurred.

Revenue recognition

Leases and lease inducements

All other leases are accounted for as operating leases wherein rental payments are expensed as incurred.

Research and development costs

Net loss attributable to common shareholders per share

Government grants and refundable investment tax credits

Government grants and tax credits provided for current expenses are included in the determination of income or loss for the year, as a reduction of the expenses to which they relate.

Deferred income taxes

Equity and liability classified stock option awards

Equity classified stock option awards

The fair value of equity classified stock options is measured at the grant date and amortized on a straight-line basis over the vesting period.

Liability-classified stock option awards

Recent accounting pronouncements

Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Schedule of assets and liabilities measured at fair value on a recurring basis



	Level 1		Level 2	Level 3	December 31, 2017
Assets
Cash and cash equivalents	$	54,292	—	—	$	54,292
Short-term investments	72,060		—	—	72,060
Restricted investment	12,601		—	—	12,601
Total	$	138,953	—	—	$	138,953
Liabilities
Liability-classified stock option awards	—		—	1,239	1,239
Contingent consideration	—		—	10,424	10,424
Total	—		—	11,663	$	11,663



	Level 1		Level 2	Level 3		December 31, 2016
Assets
Cash and cash equivalents	$	23,413	—	—		$	23,413
Guaranteed investment certificates	107,146		—	—		107,146
Term deposit	12,601		—	—		12,601
Total	$	143,160	—	—		$	143,160
Liabilities
Warrants	—		—	$	107	$	107
Liability-classified stock option awards				553		553
Contingent consideration	—		—	9,065		9,065
Total	—		—	$	9,725	$	9,725

Changes in fair value of warrants

The following table presents the changes in fair value of the Company’s warrants:



	Liability at beginning of the period		Fair value of warrants exercised in the period			Increase (decrease) in fair value of warrants			Foreign exchange loss			Liability at end of the period
Year ended December 31, 2015	$	5,099	$	(334	)	$	(3,341	)	$	(541	)	$	883
Year ended December 31, 2016	$	883	$	(247	)	$	(529	)	$	—		$	107
Year ended December 31, 2017	$	107	$	(129	)	$	22		$	—		$	—

Changes in fair value of liability-classified stock options

The following table presents the changes in fair value of the Company’s liability-classified stock option awards:



	Liability at beginning of the period		Reclassification of equity to liability ⁽¹⁾		Fair value of liability-classified stock option awards exercised in the period			Increase (decrease) in fair value of liability			Liability at end of the period
Year ended December 31, 2016	$	—	$	1,909	$	(54	)	$	(1,302	)	$	553
Year ended December 31, 2017	$	553	$	—	$	(103	)	$	789		$	1,239

(1) Upon functional currency conversion on January 1, 2016 - see functional currency conversion above.

Changes in fair value of contingent consideration

The following table presents the changes in fair value of the Company’s contingent consideration:



	Contingent consideration at beginning of the period		Increase in fair value of contingent consideration		Contingent consideration at end of the period
Year ended December 31, 2015⁽¹⁾	$	6,727	$	770	$	7,497
Year ended December 31, 2016	$	7,497	$	1,568	$	9,065
Year ended December 31, 2017	$	9,065	$	1,359	$	10,424

(1) As at acquisition date of March 4, 2015.

Property and equipment estimated useful lives

The Company records depreciation using the straight-line method over the estimated useful lives of the capital assets as follows:



	Useful life (years)
Laboratory equipment		5
Computer and office equipment	2	—	5
Furniture and fixtures		5

Schedule of basic and diluted net income (loss) per common share

The following table sets out the computation of basic and diluted net loss attributable to common shareholders per share:



	For the year ended December 31
	2017					2016			2015
Numerator:	Common Shares			Preferred Shares		Common Shares			Common Shares
Allocation of distributable earnings	$	—		$	911	$	—		$	—
Allocation of undistributed earnings (loss)	(85,324		)	—		(384,164		)	(62,718		)
Allocation of earnings (loss) attributed to shareholders	$	(85,324	)	$	911	$	(384,164	)	$	(62,718	)
Denominator:
Weighted average number of shares - basic and diluted	54,723,272			104,110		53,074,401			45,462,324
Basic and diluted net loss attributable to shareholders per share	$	(1.56	)	$	8.75	$	(7.24	)	$	(1.38	)

Impairment Evaluations For Intangible Assets and Goodwill (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of carrying values, net of impairment of the intangible assets

The following table summarizes the carrying values, net of impairment of the intangible assets as at December 31, 2017:



Year ended December 31	2017		2016
IPR&D – Immune Modulators	—		40,798
IPR&D – Antigen Inhibitors	14,811		14,811
IPR&D – cccDNA Sterilizers	43,836		43,836
Total IPR&D	$	58,647	$	99,445

Collaborations, Contracts and Licensing Agreements (Tables)

12 Months Ended

Dec. 31, 2017

Deferred Revenue Disclosure [Abstract]

Schedule of revenue recognized under collaborations, contracts and licensing agreements

The following tables set forth revenue recognized under collaborations, contracts and licensing agreements:



	Year ended December 31
	2017		2016		2015
Alexion (a)	$	7,956	$	—	$	—
Gritstone (b)	2,499		—		—
Dicerna (c)	—		1,295		2,873
Monsanto (d)	—		—		13,384
DoD (e)	—		—		6,764
Other milestone and royalty payments (f)	245		196		255
Total revenue	$	10,700	$	1,491	$	23,276

(a) License Agreement with Alexion

(b) License agreement with Gritstone

(d) Option and Services Agreements with Monsanto

(e) Contract with United States Government’s Department of Defense (“DoD”) to develop TKM-Ebola

On July 14, 2010, the Company signed a contract with the DoD to advance TKM-Ebola, an RNAi therapeutic utilizing the Company’s lipid nanoparticle technology to treat Ebola virus infection.

(f) Agreements with Spectrum Pharmaceuticals, Inc. (“Spectrum”)

Schedule of deferred collaborations and contracts revenue

(a) License Agreement with Alexion

(b) License agreement with Gritstone

(d) Option and Services Agreements with Monsanto

(e) Contract with United States Government’s Department of Defense (“DoD”) to develop TKM-Ebola

On July 14, 2010, the Company signed a contract with the DoD to advance TKM-Ebola, an RNAi therapeutic utilizing the Company’s lipid nanoparticle technology to treat Ebola virus infection.

(f) Agreements with Spectrum Pharmaceuticals, Inc. (“Spectrum”)

The following table sets forth deferred collaborations and contracts revenue:



	December 31, 2017		December 31, 2016
Gritstone (b)	$	2,727	$	—
DoD (e)	15		15
Deferred revenue, current portion	2,742		15
Total deferred revenue	$	2,742	$	15

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Schedule of property and equipment



December 31, 2017	Cost		Accumulated depreciation			Net book value
Lab equipment	$	9,567	$	(5,325	)	$	4,242
Leasehold improvements	12,578		(5,139		)	7,439
Computer hardware and software	2,318		(1,878		)	440
Furniture and fixtures	391		(329		)	62
Assets under construction	$	—				$	—
	$	24,854	$	(12,671	)	$	12,183



December 31, 2016	Cost		Accumulated depreciation			Net book value
Lab equipment	$	7,894	$	(4,305	)	$	3,589
Leasehold improvements	4,928		(4,454		)	474
Computer hardware and software	2,103		(1,665		)	438
Furniture and fixtures	374		(314		)	60
Assets under construction	$	2,384	$	—		$	2,384
	$	17,683	$	(10,738	)	$	6,945

Share Capital (Tables)

12 Months Ended

Dec. 31, 2017

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of warrant activity

The following table summarizes the Company’s warrant activity for the years ended December 31, 2017 and 2016:



	Common shares purchasable upon exercise of warrants		Weighted average exercise price		Range of exercise prices					Weighted average remaining contractual life (years)	Aggregate intrinsic value
Balance, December 31, 2015	379,500		$	2.13	$2.03		—	$	2.62	0.8	$	879
Exercised	(170,500	)	2.53		2.53		—	2.53
Expired	(8,000	)	2.53		2.53		—	2.53
Balance, December 31, 2016	201,000		$	1.94	$	1.94	—	$	1.94	0.2	$	104
Exercised	(179,000	)	2.00		$	2.00	—	$	2.00
Expired	(22,000	)	2.00		$	2.00	—	$	2.00
Balance, December 31, 2017	—		—		—		—	—		—	$	—

Schedule of stock option activity for the Arbutus Plans

Equity-classified stock option activity:



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value
Balance, December 31, 2014	1,530,138		6.29		15,004
Options granted	1,309,625		16.57
Options exercised	(398,293	)	3.93		5,386
Options forfeited, canceled or expired	(151,207	)	15.09
Balance, December 31, 2015	2,290,263		11.22		994
Options reclassified to liability¹	(718,333	)	5.23		604
Options granted	1,789,599		3.89
Options exercised	(56,125	)	2.18		121
Options forfeited, canceled or expired	(394,200	)	10.18
Balance, December 31, 2016	2,911,204		$	8.53	$	56
Options granted	2,026,500		$	3.20
Options exercised	(11,105	)	$	3.45	$	13
Options forfeited, canceled or expired	(208,272	)	$	11.41
Balance, December 31, 2017	4,718,327		$	6.06	$	5,842


1.	Due to the change in the Company's functional currency as of January 1, 2016, certain stock option awards with exercise prices denominated in Canadian dollars changed from equity classification to liability classification - see note 2.

Summary of stock options outstanding by exercise price range

The following table summarizes information pertaining to stock options outstanding at December 31, 2017 under the Arbutus Plans:



			Options outstanding December 31, 2017				Options exercisable December 31, 2017
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price (US$)		Number of options exercisable	Weighted average exercise price (US$)
$1.19	to	$3.11	114,887	5.5	2.33		83,887	2.10
$3.12	to	$3.22	1,807,000	9.2	3.15		—	N/A
$3.23	to	$3.92	368,763	8.8	3.58		186,096	3.57
$3.93	to	$3.95	1,313,682	8.2	3.94		432,365	3.94
$3.96	to	$14.32	479,537	7.0	10.48		382,701	9.97
$14.33	to	$16.16	5,500	6.6	14.74		5,500	14.74
$16.17	to	$17.57	628,958	7.2	17.57		429,582	17.57
$1.19	to	$17.57	4,718,327	8.3	$	6.06	1,520,131	$	9.20

Schedule of non-vested stock option activity

A summary of the Company’s non-vested stock option activity and related information for the year ended December 31, 2017 is as follows:



	Number of optioned common shares		Weighted average fair value
Non-vested at December 31, 2016	2,211,963		$	5.34
Options granted	2,026,500		2.15
Options vested	(972,723	)	5.82
Non-vested options forfeited	(67,544	)	4.73
Non-vested at December 31, 2017	3,198,196		$	3.23

Schedule of weighted average option pricing assumptions and the resultant fair values

The weighted average option pricing assumptions for options granted during the year are as follows:



	Year ended December 31
	2017		2016		2015
Dividend yield	—	%	—	%	—	%
Expected volatility	73.05	%	77.99	%	76.88	%
Risk-free interest rate	1.28	%	0.90	%	1.10	%
Expected average option term	6.9 years		7.3 years		7.5 years

Schedule of allocation of stock-based compensation

The total stock-based compensation has been recorded in the consolidated statement of operations and comprehensive income (loss) as follows:



	Year ended December 31
	2017		2016		2015
Research, development, collaborations and contracts expenses	$	9,236	$	11,155	$	7,868
General and administrative expenses	5,881		28,004		14,225
Total	$	15,117	$	39,159	$	22,093

Protiva Option Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of option activity

The following table sets forth outstanding options under the Protiva Option Plan:



	Number of Protiva Options		Equivalent number of Company common shares		Weighted average exercise price (C$)		Weighted average exercise price (US$)
Balance, December 31, 2014	433,740		292,845		$	0.30	0.27
Options exercised	(358,675	)	(242,164	)	0.30		0.23
Options forfeited, canceled or expired	(8,065	)	(5,445	)	0.30		0.23
Balance, December 31, 2015	67,000		45,236		0.30		0.22
Options exercised	(21,000	)	(14,178	)	0.30		0.23
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2016	46,000		31,058		0.30		0.22
Options exercised	(6,000	)	(4,051	)	0.30		0.23
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2017	40,000		27,007		$	0.30	$	0.24

OnCore Option Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of non-vested stock option activity

A summary of the OnCore Option Plan's non-vested stock option activity and related information for the year ended December 31, 2017 is as follows:



	Number of OnCore Options		Equivalent number of Company common shares		Weighted average fair value (US$)
Non-vested at December 31, 2016	63,051		63,497		$	16.80
Options vested	(30,923	)	(31,143	)	16.17
Non-vested options forfeited	—		—		N/A
Non-vested at December 31, 2017	32,128		32,354		$	16.18

Schedule of option activity

The following table sets forth outstanding options under the OnCore Option Plan:



	Number of OnCore Options	Equivalent number of Company common shares	Weighted average exercise price (US$)
Balance, December 31, 2016	183,040	184,332	$	0.57
Options exercised	—	—	N/A
Options forfeited, canceled or expired	—	—	N/A
Balance, December 31, 2017	183,040	184,332	$	0.57

Liability classified stock options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of stock option activity for the Arbutus Plans

Stock option activity for liability options



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value
Balance, December 31, 2016	638,500		$	5.48	$	116
Options exercised	(25,000	)	2.37		103
Options forfeited, canceled, or expired	(162,000	)	6.54		—
Balance, December 31, 2017	451,500		$	5.78	$	525

Schedule of weighted average Black-Scholes option-pricing assumptions and resultant fair values

The weighted average Black-Scholes option-pricing assumptions and the resultant fair values as at December 31, 2016 and December 31, 2017, are presented in the following table:



	December 31,			December 31,
	2017			2016
Dividend yield	—		%	—		%
Expected volatility	70.31		%	66.18		%
Risk-free interest rate	2.10		%	0.88		%
Expected average term (years)	4.3			3.6
Fair value of options outstanding	$	2.75		$	0.87
Fair value of vested liability-classified options (in thousands)	$	1,239		$	553

Summary of stock options outstanding by exercise price range

The following table summarizes information pertaining to liability options outstanding at December 31, 2017:



			Options outstanding December 31, 2017				Options exercisable December 31, 2017
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price		Number of options exercisable	Weighted average exercise price
$1.35	to	$1.67	65,000	2.8	$	1.38	65,000	$	1.38
$1.68	to	$3.38	75,000	2.9	2.45		75,000	2.45
$3.39	to	$4.27	75,000	3.2	3.94		75,000	3.94
$4.28	to	$5.85	14,000	0.3	4.45		14,000	4.45
$5.86	to	$8.61	150,000	5.8	7.25		150,000	7.25
$8.62	to	$13.04	72,500	6.2	12.30		72,500	12.30
$1.35	to	$13.04	451,500	4.3	$	5.78	451,500	$	5.78

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of effective income tax rate reconciliation



	Year ended December 31,
	2017			2016			2015
Computed taxes (recoveries) at Canadian federal and provincial tax rates	$	(28,270	)	$	(127,183	)	$	(20,100	)
Difference due to change in tax rate on opening deferred taxes	(6,633		)	—			—
Permanent and other differences	1,476			(3,598		)	769
Change in valuation allowance - other	6,945			17,043			3,675
Difference due to income taxed at foreign rates	(966		)	(47,962		)	(7,874		)
Stock-based compensation	3,128			9,727			7,345
Impairment of goodwill	—			46,971			—
Deferred income tax recovery	$	(24,320	)	$	(105,002	)	$	(16,185	)

Schedule of components of deferred tax assets

Significant components of the Company’s deferred tax assets and liabilities are shown below:



	As at December 31,
	2017			2016
Deferred tax assets (liabilities):
Non-capital loss carryforwards	$	36,652		$	24,275
Research and development deductions	16,603			16,986
Book amortization in excess of tax	(650		)	451
Share issue costs	456			486
Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes	1,162			410
Tax value in excess of accounting value in lease inducements	173			58
Federal investment tax credits	9,079			8,630
Provincial investment tax credits	4,819			5,270
In-process research and development	(16,943		)	(41,263		)
Upfront license fees	311			536
Other	2,017			1,435
Total deferred tax assets (liabilities)	53,679			17,274
Valuation allowance	(70,622		)	(58,537		)
Net deferred tax assets (liabilities)	$	(16,943	)	$	(41,263	)

Concentrations of Business Risk (Tables)

12 Months Ended

Dec. 31, 2017

Risks and Uncertainties [Abstract]

Net liquidity

The net liquidity of the Company is considered to be the cash and cash equivalents and short-term investments less accounts payable and accrued liabilities.



	December 31, 2017			December 31, 2016
Cash, cash equivalents and short-term investments	$	126,352		$	130,559
Less: Accounts payable and accrued liabilities	$	(10,646	)	$	(9,910	)
	$	115,706		$	120,649

Schedule of exposure to US dollar currency expressed in Canadian dollars

The Company’s exposure to Canadian dollar currency expressed in US dollars was as follows:



(in US$)	December 31, 2017			December 31, 2016
Cash and cash equivalents and short-term investments	$	25,921		$	43,094
Accounts receivable	375			289
Accrued revenue	—			128
Accounts payable and accrued liabilities	(1,273		)	(3,238		)
	$	25,023		$	40,273

Interim Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of interim financial data (unaudited)



	2017
	Q1			Q2			Q3			Q4			Total
Revenue	$	235		$	1,039		$	6,892		$	2,534		$	10,700
Loss from operations	(18,299		)	(19,485		)	(12,897		)	(60,249		)	(110,930		)
Net loss	$	(18,627	)	$	(18,255	)	$	(11,600	)	$	(35,931	)	$	(84,413	)
Basic and diluted net loss per common share	$	(0.34	)	$	(0.33	)	$	(0.21	)	$	(0.67	)	$	(1.56	)



	2016
	Q1			Q2			Q3			Q4			Total
Revenue	$	603		$	309		$	774		$	(195	)	$	1,491
Loss from operations	(19,977		)	(195,248		)	(18,975		)	(257,439		)	(491,639		)
Net loss	$	(15,874	)	$	(130,000	)	$	(19,595	)	$	(218,695	)	$	(384,164	)
Basic and diluted net loss per common share	$	(0.31	)	$	(2.47	)	$	(0.37	)	$	(4.05	)	$	(7.24	)

Significant Accounting Policies - Narrative (Details)			10 Months Ended	12 Months Ended
Significant Accounting Policies - Narrative (Details)	Jan. 12, 2018 shares	Oct. 02, 2017	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) subsidiary shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Mar. 04, 2016	Mar. 04, 2015 USD ($)
Accounting Policies [Abstract]
Wholly-owned subsidiaries \| subsidiary				2
Business Acquisition [Line Items]
Cumulative Translation Adjustment, Net of Tax, Period Increase (Decrease) \| $						$ 1,597,000
Restricted investment, term				2 years
Interest rate on restricted investment				1.25%
Fair value of contingent consideration \| $			$ 7,497,000	$ 10,424,000	$ 9,065,000	7,497,000		$ 6,727,000
Increase in fair value of contingent consideration \| $			$ 770,000	$ 1,359,000	$ 1,568,000	$ 770,000
Class of Stock [Line Items]
Anti-dilutive common shares excluded from calculation of income per common share (in shares) \| shares				12,521,550	4,645,864	2,899,331
Subsequent event
Class of Stock [Line Items]
Anti-dilutive common shares excluded from calculation of income per common share (in shares) \| shares	21,878,002
Incremental common shares attributable to dilutive effect of conversion of preferred stock \| shares	664,000
Convertible Preferred Stock \| Roivant Sciences Ltd
Class of Stock [Line Items]
Preferred dividend percentage		8.75%		8.75%
PADCo. \| Monsanto
Business Acquisition [Line Items]
Business acquisition, percentage of outstanding shares acquired							100.00%

Significant Accounting Policies - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 04, 2015	Dec. 31, 2014
Assets
Cash and cash equivalents	$ 54,292	$ 23,413
Short-term investments and guaranteed investment certificates	72,060	107,146
Restricted investment	12,601	12,601
Total Assets	138,953	143,160
Liabilities
Warrants	0	107	$ 883		$ 5,099
Liability-classified stock option awards	1,239	553
Contingent consideration	10,424	9,065	$ 7,497	$ 6,727
Total Liabilities	11,663	9,725
Fair value, inputs, Level 1
Assets
Cash and cash equivalents	54,292	23,413
Short-term investments and guaranteed investment certificates	72,060	107,146
Restricted investment	12,601	12,601
Total Assets	138,953	143,160
Fair value, inputs, Level 3
Liabilities
Warrants		107
Liability-classified stock option awards	1,239	553
Contingent consideration	10,424	9,065
Total Liabilities	$ 11,663	$ 9,725

Significant Accounting Policies - Changes in Fair Value of the Company's Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 107	$ 883	$ 5,099
Fair value of warrants exercised in the period	(129)	(247)	(334)
Increase (decrease) in fair value of warrants	22	(529)	(3,341)
Foreign exchange loss	0	0	(541)
Liability at end of the period	$ 0	$ 107	$ 883

Significant Accounting Policies - Changes in Fair Value of Liability-Classified Stock Options (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 553
Liability at end of the period	1,239	$ 553
Liability classified stock options
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	553	1,909
Fair value of liability-classified stock option awards exercised in the period	(103)	(54)
Increase (decrease) in fair value of liability	789	(1,302)
Liability at end of the period	$ 1,239	$ 553

Significant Accounting Policies - Changes in Fair Value of Contingent Consideration (Details) - USD ($) $ in Thousands	10 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration Fair Value, Liability [Roll Forward]
Contingent consideration at beginning of the period	$ 6,727	$ 9,065	$ 7,497
Increase in fair value of contingent consideration	770	1,359	1,568	$ 770
Contingent consideration at end of the period	$ 7,497	$ 10,424	$ 9,065	$ 7,497

Significant Accounting Policies - Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2017
Laboratory equipment
Property, Plant and Equipment [Line Items]
Useful lives	5 years
Computer and office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful lives	2 years
Computer and office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful lives	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful lives	5 years

Significant Accounting Policies - Computation of Basic and Diluted Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Allocation of distributable earnings									$ 911	$ 0	$ 0
Allocation of earnings (loss) attributed to shareholders									$ (85,324)	$ (384,164)	(62,718)
Basic and diluted net loss attributable to shareholders per share (USD per share)	$ (0.67)	$ (0.21)	$ (0.33)	$ (0.34)	$ (4.05)	$ (0.37)	$ (2.47)	$ (0.31)	$ (1.56)	$ (7.24)
Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Allocation of earnings (loss) attributed to shareholders									$ (85,324)	$ (384,164)	$ (62,718)
Weighted average number of shares - basic diluted (in shares)									54,723,272	53,074,401	45,462,324
Basic and diluted net loss attributable to shareholders per share (USD per share)									$ (1.56)	$ (7.24)	$ (1.38)
Preferred Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Allocation of distributable earnings									$ 911
Allocation of earnings (loss) attributed to shareholders									$ 911
Weighted average number of shares - basic diluted (in shares)									104,110
Basic and diluted net loss attributable to shareholders per share (USD per share)									$ 8.75

Impairment Evaluations For Intangible Assets and Goodwill - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) reporting_unit	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Impairment charge	$ 40,798	$ 253,197	$ 39,007
Income tax benefit on impairment charge	$ 24,320	105,002	16,185
Number of reporting units \| reporting_unit	1
Goodwill	$ 24,364	24,364
Goodwill impairment charge	0	138,150	$ 0
STING Drug Candidate [Member]
Indefinite-lived Intangible Assets [Line Items]
Impairment charge	40,798
Income tax benefit on impairment charge	$ 16,926
Immune Modulator and cccDNA Sterilizer drug classes
Indefinite-lived Intangible Assets [Line Items]
Impairment charge		$ 96,873

Impairment Evaluations For Intangible Assets and Goodwill - Summary of carrying value of intangible assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	$ 58,647	$ 99,445
IPR&D – Immune Modulators
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	0	40,798
IPR&D – Antigen Inhibitors
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	14,811	14,811
IPR&D – cccDNA Sterilizers
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	$ 43,836	$ 43,836

Collaborations, Contracts and Licensing Agreements - Revenue Recognized Under Collaborations, Contracts and Licensing Agreements (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue	$ 2,534	$ 6,892	$ 1,039	$ 235	$ (195)	$ 774	$ 309	$ 603	$ 10,700	$ 1,491	$ 23,276
Alexion
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									7,956	0	0
Gritstone
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									2,499	0	0
Dicerna
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									0	1,295	2,873
Monsanto
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									0	0	13,384
DoD
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									0	0	6,764
Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									$ 245	$ 196	$ 255

Collaborations, Contracts and Licensing Agreements - Deferred Collaborations and Contracts Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current portion	$ 2,742	$ 15
Total deferred revenue	2,742	15
Gritstone
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current portion	2,727	0
DoD
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current portion	$ 15	$ 15

- Definition

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

+ References + Details

Collaborations, Contracts and Licensing Agreements - Narrative (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2012 USD ($)	Mar. 16, 2017 USD ($)	Mar. 04, 2016 USD ($)	Nov. 16, 2014 USD ($)	May 06, 2006 chemotherapy_products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue	$ 2,742,000				$ 15,000				$ 2,742,000	$ 15,000
Licensing fees, milestone and royalty payments									10,018,000	1,262,000	$ 11,564,000
Revenue	2,534,000	$ 6,892,000	$ 1,039,000	$ 235,000	$ (195,000)	$ 774,000	$ 309,000	$ 603,000	10,700,000	1,491,000	23,276,000
Number of chemotherapy products with worldwide licenses \| chemotherapy_products																3
Contracts revenue									682,000	229,000	11,712,000
Alexion
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License Upfront Payment													$ 7,500,000
Revenue									7,956,000	0	0
Dicerna
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue															$ 2,500,000
Licensing fees, milestone and royalty payments									0	1,066,000
Revenue									0	1,295,000	2,873,000
Monsanto
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue									0	0	13,384,000
Talon Therapeutics
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential contract funding amount												$ 18,000,000
Marqibo Commercial Sales
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contracts revenue												$ 1,000,000
Marqibo
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty revenue									191,000	$ 212,000	$ 240,000
Accrued royalties	$ 5,000								$ 5,000
PADCo. \| Monsanto
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Business acquisition, percentage of outstanding shares acquired														100.00%
Optional exercised contractual option, amount														$ 1,000,000

Property and Equipment - Property and Equipment Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Cost	$ 24,854	$ 17,683
Accumulated depreciation	(12,671)	(10,738)
Property and equipment, net of accumulated depreciation	12,183	6,945
Lab equipment
Property, Plant and Equipment [Line Items]
Cost	9,567	7,894
Accumulated depreciation	(5,325)	(4,305)
Property and equipment, net of accumulated depreciation	4,242	3,589
Leasehold improvements
Property, Plant and Equipment [Line Items]
Cost	12,578	4,928
Accumulated depreciation	(5,139)	(4,454)
Property and equipment, net of accumulated depreciation	7,439	474
Computer hardware and software
Property, Plant and Equipment [Line Items]
Cost	2,318	2,103
Accumulated depreciation	(1,878)	(1,665)
Property and equipment, net of accumulated depreciation	440	438
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Cost	391	374
Accumulated depreciation	(329)	(314)
Property and equipment, net of accumulated depreciation	62	60
Assets under construction
Property, Plant and Equipment [Line Items]
Cost	0	2,384
Property and equipment, net of accumulated depreciation	$ 0	$ 2,384

Share Capital - Narrative: Financing and Authorized Share Capital (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Mar. 25, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Stock issued during underwritten public offering (in shares)	7,500,000
Stock price at public offering (in USD per share)	$ 20.25
Proceeds from issuance of common shares, net of issuance costs	$ 151,875	$ 0	$ 0	$ 142,177
Period for option to purchase additional shares	30 days
Options granted (in shares)	1,125,000	2,026,500
Potential proceeds of additional shares authorized	$ 22,781
Payments of stock issuance costs, including commissions and professional fees	9,700
Proceeds from issuance of common stock, net	$ 142,177
Preferred stock, shares authorized (in shares)		1,164,000	0

Share Capital - Narrative: Preferred Shares (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Jan. 12, 2018	Oct. 16, 2017	Oct. 02, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 29, 2017
Class of Stock [Line Items]
Issuance of common shares in conjunction with the private offering, net of issuance costs						$ 142,177
Share Price							$ 6.20
Proceeds from sale of Preferred Shares, net of issuance costs				$ 48,869	$ 0	$ 0
Roivant Sciences Ltd
Class of Stock [Line Items]
Noncontrolling Interest, Ownership Percentage By Noncontrolling Owners After Conversion			49.90%
Noncontrolling Interest, Maximum Ownership Percentage by Noncontrolling Owners			49.99%
Proceeds from sale of Preferred Shares, net of issuance costs		$ 50,000
Roivant Sciences Ltd \| Convertible Preferred Stock
Class of Stock [Line Items]
Issuance of common shares in conjunction with the private offering, net of issuance costs			$ 116,400
Preferred Stock, par value (USD per share)			$ 7.13
Premium on closing stock price							15.00%
Preferred dividend percentage			8.75%	8.75%
Noncontrolling Interest, Investment Commitment Period			4 years
Subsequent Event \| Roivant Sciences Ltd
Class of Stock [Line Items]
Proceeds from sale of Preferred Shares, net of issuance costs	$ 66,400
Subsequent Event \| Roivant Sciences Ltd \| Convertible Preferred Stock
Class of Stock [Line Items]
Issuance of common shares in conjunction with the private offering, net of issuance costs	$ 116,400

Share Capital - Narrative: Warrants to Purchase Common Shares (Details) - USD ($) $ in Thousands		12 Months Ended
	Mar. 01, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Warrant or Right [Line Items]
Warrants exercised (in shares)		179,000	170,500
Proceeds from warrant exercises		$ 353	$ 445	$ 42
Common shares issued from warrants exercise (in shares)			0
Warrants expired (in shares)	22,000	22,000	8,000
Cashless Exercise Provision
Class of Warrant or Right [Line Items]
Warrants exercised (in shares)		0	0

Share Capital - Narrative: Stock-based Compensation (Details)						12 Months Ended
	May 19, 2016 shares	Mar. 25, 2015 shares	Mar. 04, 2015 USD ($) shares	Jun. 22, 2011	May 30, 2008 $ / shares shares	Dec. 31, 2017 USD ($) compensation_plan $ / shares shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 executive_officers shares	Jul. 09, 2015 shares	May 08, 2014 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans \| compensation_plan						7
Number of stock-based compensation awards approved to be issued (in shares)						5,084,189					3,500,000	800,000
Number of additional shares authorized (in shares)	5,000,000
Options granted (in shares)		1,125,000				2,026,500
Number of executive officers granted options with new appointments \| executive_officers										2
Options exercisable (in shares)						1,520,131	699,241	699,241	938,730
Weighted average remaining contractual life of exercisable options						7 years 5 months 5 days
Options exercisable, intrinsic value \| $						$ 1,098,000
Weighted average remaining contractual life for options expected to vest						8 years 3 months 26 days
Average exercise price for options expected to vest (in CAD and USD per share) \| $ / shares						$ 6.06
Aggregate intrinsic value of option expected to vest \| $						$ 5,842,000	$ 0	$ 0	$ 10,000
Total fair value of options that vested during period \| $						$ 5,657,000	5,058,000		1,718,000
Options vested (in shares)						972,723
Business acquisition, post-combination attribution recognized as compensation expense \| $			$ 56,934,000
Stock-based compensation expense \| $						$ 15,117,000	$ 39,159,000		22,093,000
Unearned compensation expense \| $						$ 5,747,000
Unearned compensation expense, recognition period						1 year 8 months
Number of options outstanding (in shares)						5,381,163
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average term (years)						4 years 3 months 30 days	3 years 7 months 6 days
Average exercise price for options expected to vest (in CAD and USD per share) \| $ / shares						$ 12.83
Total fair value of options that vested during period \| $						$ 36,100
Options vested (in shares)						14,750
Options exercised, aggregate intrinsic value \| $						$ 103,000		$ 54,000
Number of options outstanding (in shares)						451,500	638,500	638,500
Expired repurchase rights on shares issued to Arbutus Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense \| $						$ 7,972,000	$ 31,986,000		$ 16,687,000
2007 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period				3 years
2007 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average term (years)				10 years
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period				3 years
2011 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average term (years)				10 years
Designated Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)										200,000
Arbutus Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average term (years)						6 years 10 months 28 days	7 years 3 months 18 days		7 years 6 months
Options granted (in shares)						2,026,500	1,789,599		1,309,625
Risk-free interest rate						0.00%
Options exercised, aggregate intrinsic value \| $						$ 13,000	$ 121,000		$ 5,386,000
Number of options outstanding (in shares)						4,718,327	2,911,204	2,911,204	2,290,263	1,530,138
Protiva Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future exercise (in shares)					350,457
Option exercise price (in CAD per share) \| $ / shares					$ 0.30
Conversion of stock, shares converted (in shares)					0.6752
Protiva Option Plan \| Revised new common shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future exercise (in shares)					519,073
Protiva Option Plan \| Protiva Share Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining contractual life of exercisable options						1 month 28 days
Options exercisable, intrinsic value \| $						$ 127,000
Options exercised, aggregate intrinsic value \| $						$ 10,000	$ 49,000		$ 1,249,000
OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation awards approved to be issued (in shares)			184,332
Options exercisable (in shares)						150,913
Weighted average remaining contractual life of exercisable options						6 years 10 months 24 days
Options exercisable, intrinsic value \| $						$ 682,000
Weighted average remaining contractual life for options expected to vest						6 years 10 months 24 days
Average exercise price for options expected to vest (in CAD and USD per share) \| $ / shares						$ 0.57
Aggregate intrinsic value of option expected to vest \| $						$ 144,000
Total fair value of options that vested during period \| $						$ 611,000
Risk-free interest rate			0.97%
Options vested (in shares)						30,923
Fair value of consideration issued \| $			$ 3,287,000
Expected volatility			78.00%
Dividend yield			0.00%
Expected average term (years)			8 years
Business acquisition, fair value amount attributed as pre-combination service and included as part of acquisition consideration \| $			$ 1,127,000
Business acquisition, post-combination attribution recognized as compensation expense \| $			$ 2,160,000
Stock-based compensation expense \| $						$ 576,000
Options exercisable weighted average exercise price (in USD per share) \| $ / shares						$ 0.56
Number of options outstanding (in shares)						183,040	183,040	183,040
OnCore Option Plan \| Equivalent number of Company common shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (in shares)						151,978
Options vested (in shares)						31,143
Number of options outstanding (in shares)						184,332	184,332	184,332

Share Capital - Summary of Warrant Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Mar. 01, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights [Roll Forward]
Balance, Common shares purchasable upon exercise of warrants (in shares)		201,000	379,500
Exercised, Common shares purchasable upon exercise of warrants (in shares)		(179,000)	(170,500)
Expired, Common shares purchasable upon exercise of warrants (in shares)	(22,000)	(22,000)	(8,000)
Balance, Common shares purchasable upon exercise of warrants (in shares)		0	201,000	379,500
Balance, Weighted average exercise price (USD per share)		$ 1.94	$ 2.13
Exercised, Weighted average exercise price (USD per share)		2.00	2.53
Expired, Weighted average exercise price (USD per share)		2.00	2.53
Balance, Weighted average exercise price (USD per share)		$ 0.00	$ 1.94	$ 2.13
Balance, Weighted average remaining contractual life		0 years	2 months 12 days	9 months 18 days
Aggregate intrinsic value		$ 0	$ 104	$ 879
Minimum
Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights [Roll Forward]
Balance, Range of exercise prices (USD per share)		$ 1.94	$ 2.03
Exercised, Range of exercise prices (USD per share)		2.00	2.53
Expired, Range of exercise prices (USD per share)		2.00	2.53
Balance, Range of exercise prices (USD per share)		0.00	1.94	$ 2.03
Maximum
Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights [Roll Forward]
Balance, Range of exercise prices (USD per share)		1.94	2.62
Exercised, Range of exercise prices (USD per share)		2.00	2.53
Expired, Range of exercise prices (USD per share)		2.00	2.53
Balance, Range of exercise prices (USD per share)		$ 0.00	$ 1.94	$ 2.62

Share Capital - Summary of Information - Equity Options (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Mar. 25, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options granted (in shares)	1,125,000	2,026,500
Balance - Number of optioned common shares (in shares)		5,381,163
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options reclassified liability - Weighted average exercise price (in CAD and USD per share)			$ 5.23
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options reclassified - Aggregate intrinsic value			$ 604
Arbutus Plans
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)		2,911,204	2,290,263	1,530,138
Options reclassified to liability (in shares)			(718,333)
Options granted (in shares)		2,026,500	1,789,599	1,309,625
Options exercised (in shares)		(11,105)	(56,125)	(398,293)
Options forfeited, canceled or expired (in shares)		(208,272)	(394,200)	(151,207)
Balance - Number of optioned common shares (in shares)		4,718,327	2,911,204	2,290,263
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Balance - Weighted average exercise price (in CAD and USD per share)		$ 8.53	$ 11.22	$ 6.29
Options granted - Weighted average exercise price (in CAD and USD per share)		3.20	3.89	16.57
Options exercised - Weighted average exercise price (in CAD and USD per share)		3.45	2.18	3.93
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share)		11.41	10.18	15.09
Balance - Weighted average exercise price (in CAD and USD per share)		$ 6.06	$ 8.53	$ 11.22
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Balance - Aggregate intrinsic value		$ 56	$ 994	$ 15,004
Options exercised, aggregate intrinsic value		13	121	5,386
Balance - Aggregate intrinsic value		$ 5,842	$ 56	$ 994

Share Capital - Stock Options Outstanding - Equity Options (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Range 1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	$ 1.19
Range of Exercise prices - High (in USD per share)	$ 3.11
Number of options outstanding (in shares) \| shares	114,887
Weighted average remaining contractual life (years)	5 years 6 months 11 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 2.33
Number of options exercisable (in shares) \| shares	83,887
Weighted average exercise price (in USD per share)	$ 2.10
Range 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	3.12
Range of Exercise prices - High (in USD per share)	$ 3.22
Number of options outstanding (in shares) \| shares	1,807,000
Weighted average remaining contractual life (years)	9 years 2 months 23 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.15
Number of options exercisable (in shares) \| shares	0
Range 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	$ 3.23
Range of Exercise prices - High (in USD per share)	$ 3.92
Number of options outstanding (in shares) \| shares	368,763
Weighted average remaining contractual life (years)	8 years 9 months 22 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.58
Number of options exercisable (in shares) \| shares	186,096
Weighted average exercise price (in USD per share)	$ 3.57
Range 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	3.93
Range of Exercise prices - High (in USD per share)	$ 3.95
Number of options outstanding (in shares) \| shares	1,313,682
Weighted average remaining contractual life (years)	8 years 2 months 12 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.94
Number of options exercisable (in shares) \| shares	432,365
Weighted average exercise price (in USD per share)	$ 3.94
Range 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	3.96
Range of Exercise prices - High (in USD per share)	$ 14.32
Number of options outstanding (in shares) \| shares	479,537
Weighted average remaining contractual life (years)	6 years 11 months 16 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 10.48
Number of options exercisable (in shares) \| shares	382,701
Weighted average exercise price (in USD per share)	$ 9.97
Range 6
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	14.33
Range of Exercise prices - High (in USD per share)	$ 16.16
Number of options outstanding (in shares) \| shares	5,500
Weighted average remaining contractual life (years)	6 years 6 months 26 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 14.74
Number of options exercisable (in shares) \| shares	5,500
Weighted average exercise price (in USD per share)	$ 14.74
Range 7
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	16.17
Range of Exercise prices - High (in USD per share)	$ 17.57
Number of options outstanding (in shares) \| shares	628,958
Weighted average remaining contractual life (years)	7 years 2 months 27 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 17.57
Number of options exercisable (in shares) \| shares	429,582
Weighted average exercise price (in USD per share)	$ 17.57
Total Range
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	1.19
Range of Exercise prices - High (in USD per share)	$ 17.57
Number of options outstanding (in shares) \| shares	4,718,327
Weighted average remaining contractual life (years)	8 years 3 months 26 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 6.06
Number of options exercisable (in shares) \| shares	1,520,131
Weighted average exercise price (in USD per share)	$ 9.20

Share Capital - Non-vested Stock Option Activity - Equity Options (Details) - $ / shares		12 Months Ended
	Mar. 25, 2015	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Non-vested, beginning balance (in shares)		2,211,963
Options granted (in shares)	1,125,000	2,026,500
Options vested (in shares)		(972,723)
Non-vested options forfeited (in shares)		(67,544)
Non-vested, ending balance (in shares)		3,198,196
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested, beginning balance, weighted average fair value (USD per share)		$ 5.34
Options granted (USD per share)		2.15
Options vested (USD per share)		5.82
Non-vested options forfeited (USD per share)		4.73
Non-vested, ending balance, weighted average fair value (USD per share)		$ 3.23

Share Capital - Valuation Assumptions - Equity Options (Details) - Arbutus Plans	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	73.05%	77.99%	76.88%
Risk-free interest rate	1.28%	0.90%	1.10%
Expected average option term	6 years 10 months 28 days	7 years 3 months 18 days	7 years 6 months

Share Capital - Valuation Assumptions - Liability-Classified Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of vested liability-classified options (in thousands)	$ 1,239	$ 553
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility	70.31%	66.18%
Risk-free interest rate	2.10%	0.88%
Expected average term (years)	4 years 3 months 30 days	3 years 7 months 6 days
Fair value of liability options outstanding (in USD per share)	$ 2.75	$ 0.87
Fair value of vested liability-classified options (in thousands)	$ 1,239	$ 553	$ 1,909

Share Capital - Stock Option Activity for Liability-Classified Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	5,381,163
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	638,500
Options exercised (in shares)	(25,000)
Options forfeited, canceled or expired (in shares)	(162,000)
Balance - Number of optioned common shares (in shares)	451,500	638,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Balance - Weighted average exercise price (in CAD and USD per share)	$ 5.48
Options exercised - Weighted average exercise price (in CAD and USD per share)	2.37
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share)	6.54
Balance - Weighted average exercise price (in CAD and USD per share)	$ 5.78	$ 5.48
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Balance - Aggregate intrinsic value	$ 116
Options exercised, aggregate intrinsic value	103	$ 54
Balance - Aggregate intrinsic value	$ 525	$ 116

Share Capital - Summary of Information Liability-Classified Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Weighted average exercise price (in USD per share)	$ 5.78	$ 5.48
Number of options exercisable (in shares)	451,500
Weighted average exercise price (in USD per share)	$ 5.78
Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	1.19
Range of Exercise prices - High (in USD per share)	$ 3.11
Number of options outstanding (in shares)	114,887
Weighted average remaining contractual life (years)	5 years 6 months 11 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 2.33
Number of options exercisable (in shares)	83,887
Weighted average exercise price (in USD per share)	$ 2.10
Range 1 \| Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	1.35
Range of Exercise prices - High (in USD per share)	$ 1.67
Number of options outstanding (in shares)	65,000
Weighted average remaining contractual life (years)	2 years 9 months 22 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 1.38
Number of options exercisable (in shares)	65,000
Weighted average exercise price (in USD per share)	$ 1.38
Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.12
Range of Exercise prices - High (in USD per share)	$ 3.22
Number of options outstanding (in shares)	1,807,000
Weighted average remaining contractual life (years)	9 years 2 months 23 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.15
Number of options exercisable (in shares)	0
Range 2 \| Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	$ 1.68
Range of Exercise prices - High (in USD per share)	$ 3.38
Number of options outstanding (in shares)	75,000
Weighted average remaining contractual life (years)	2 years 10 months 21 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 2.45
Number of options exercisable (in shares)	75,000
Weighted average exercise price (in USD per share)	$ 2.45
Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.23
Range of Exercise prices - High (in USD per share)	$ 3.92
Number of options outstanding (in shares)	368,763
Weighted average remaining contractual life (years)	8 years 9 months 22 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.58
Number of options exercisable (in shares)	186,096
Weighted average exercise price (in USD per share)	$ 3.57
Range 3 \| Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.39
Range of Exercise prices - High (in USD per share)	$ 4.27
Number of options outstanding (in shares)	75,000
Weighted average remaining contractual life (years)	3 years 2 months 23 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.94
Number of options exercisable (in shares)	75,000
Weighted average exercise price (in USD per share)	$ 3.94
Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.93
Range of Exercise prices - High (in USD per share)	$ 3.95
Number of options outstanding (in shares)	1,313,682
Weighted average remaining contractual life (years)	8 years 2 months 12 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.94
Number of options exercisable (in shares)	432,365
Weighted average exercise price (in USD per share)	$ 3.94
Range 4 \| Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	4.28
Range of Exercise prices - High (in USD per share)	$ 5.85
Number of options outstanding (in shares)	14,000
Weighted average remaining contractual life (years)	3 months
Options outstanding, Weighted average exercise price (in USD per share)	$ 4.45
Number of options exercisable (in shares)	14,000
Weighted average exercise price (in USD per share)	$ 4.45
Range 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.96
Range of Exercise prices - High (in USD per share)	$ 14.32
Number of options outstanding (in shares)	479,537
Weighted average remaining contractual life (years)	6 years 11 months 16 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 10.48
Number of options exercisable (in shares)	382,701
Weighted average exercise price (in USD per share)	$ 9.97
Range 5 \| Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	5.86
Range of Exercise prices - High (in USD per share)	$ 8.61
Number of options outstanding (in shares)	150,000
Weighted average remaining contractual life (years)	5 years 9 months 4 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 7.25
Number of options exercisable (in shares)	150,000
Weighted average exercise price (in USD per share)	$ 7.25
Range 6
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	14.33
Range of Exercise prices - High (in USD per share)	$ 16.16
Number of options outstanding (in shares)	5,500
Weighted average remaining contractual life (years)	6 years 6 months 26 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 14.74
Number of options exercisable (in shares)	5,500
Weighted average exercise price (in USD per share)	$ 14.74
Range 6 \| Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	8.62
Range of Exercise prices - High (in USD per share)	$ 13.04
Number of options outstanding (in shares)	72,500
Weighted average remaining contractual life (years)	6 years 1 month 28 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 12.30
Number of options exercisable (in shares)	72,500
Weighted average exercise price (in USD per share)	$ 12.30
Total Range
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	1.19
Range of Exercise prices - High (in USD per share)	$ 17.57
Number of options outstanding (in shares)	4,718,327
Weighted average remaining contractual life (years)	8 years 3 months 26 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 6.06
Number of options exercisable (in shares)	1,520,131
Weighted average exercise price (in USD per share)	$ 9.20
Total Range \| Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	1.35
Range of Exercise prices - High (in USD per share)	$ 13.04
Number of options outstanding (in shares)	451,500
Weighted average remaining contractual life (years)	4 years 3 months 29 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 5.78

Share Capital - Outstanding Options Under the Protiva Option Plan (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares	Dec. 31, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	5,381,163	5,381,163
Protiva Share Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	46,000	46,000	67,000	67,000	433,740	433,740
Options exercised (in shares)	(6,000)	(6,000)	(21,000)	(21,000)	(358,675)	(358,675)
Options forfeited, canceled or expired (in shares)	0	0	0	0	(8,065)	(8,065)
Balance - Number of optioned common shares (in shares)	40,000	40,000	46,000	46,000	67,000	67,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Balance - Weighted average exercise price (in CAD and USD per share) \| (per share)	$ 0.30	$ 0.22	$ 0.30	$ 0.22	$ 0.30	$ 0.27
Options exercised - Weighted average exercise price (in CAD and USD per share) \| (per share)	0.30	0.23	0.30	0.23	0.30	0.23
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share) \| (per share)	0.00		0.00		0.30	0.23
Balance - Weighted average exercise price (in CAD and USD per share) \| (per share)	$ 0.30	$ 0.24	$ 0.30	$ 0.22	$ 0.30	$ 0.22
Equivalent number of Company common shares \| Protiva Share Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	31,058	31,058	45,236	45,236	292,845	292,845
Options exercised (in shares)	(4,051)	(4,051)	(14,178)	(14,178)	(242,164)	(242,164)
Options forfeited, canceled or expired (in shares)	0	0	0	0	(5,445)	(5,445)
Balance - Number of optioned common shares (in shares)	27,007	27,007	31,058	31,058	45,236	45,236

Share Capital - Outstanding Options Under the OnCore Option Plan (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	5,381,163
OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	183,040
Options exercised (in shares)	0
Options forfeited, canceled or expired (in shares)	0
Balance - Number of optioned common shares (in shares)	183,040
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Balance - Weighted average exercise price (in CAD and USD per share) \| $ / shares	$ 0.57
Balance - Weighted average exercise price (in CAD and USD per share) \| $ / shares	$ 0.57
Equivalent number of Company common shares \| OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance - Number of optioned common shares (in shares)	184,332
Options exercised (in shares)	0
Options forfeited, canceled or expired (in shares)	0
Balance - Number of optioned common shares (in shares)	184,332

Share Capital - Non-vested Stock Option Activity OnCore Option Plan (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Non-vested, beginning balance (in shares)	2,211,963
Options vested (in shares)	(972,723)
Non-vested options forfeited (in shares)	(67,544)
Non-vested, ending balance (in shares)	3,198,196
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested, beginning balance, weighted average fair value (USD per share) \| $ / shares	$ 5.34
Options vested (USD per share) \| $ / shares	5.82
Non-vested, ending balance, weighted average fair value (USD per share) \| $ / shares	$ 3.23
OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Non-vested, beginning balance (in shares)	63,051
Options vested (in shares)	(30,923)
Non-vested options forfeited (in shares)	0
Non-vested, ending balance (in shares)	32,128
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested, beginning balance, weighted average fair value (USD per share) \| $ / shares	$ 16.80
Options vested (USD per share) \| $ / shares	16.17
Non-vested, ending balance, weighted average fair value (USD per share) \| $ / shares	$ 16.18
Equivalent number of Company common shares \| OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Non-vested, beginning balance (in shares)	63,497
Options vested (in shares)	(31,143)
Non-vested options forfeited (in shares)	0
Non-vested, ending balance (in shares)	32,354

Share Capital - Location Of Expenses for Stock-based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 15,117	$ 39,159	$ 22,093
Research, development, collaborations and contracts expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	9,236	11,155	7,868
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 5,881	$ 28,004	$ 14,225

Income Taxes (Details) $ in Thousands, $ in Millions		12 Months Ended
Income Taxes (Details) $ in Thousands, $ in Millions	Nov. 23, 2011 CAD ($)	Dec. 31, 2018	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Income Taxes [Line Items]
Canadian federal and provincial income tax rate			26.00%	26.00%	26.00%
Provisional tax benefit as a reduction of deferred tax liabilities due to 2017 Tax Act			$ 13,400
Provisional tax expense as a reduction in tax deferred assets due to 2017 Tax Act			3,500
Patent tax refund percentage	75.00%
Research and development credits			3,639	$ 1,454
Scientific research and experimental development expenditures available for indefinite carry-forward			36,652	24,275
Deferred tax assets, operating loss carryforwards, subject to expiration			13,723	14,621
Income tax refund maximum from patents			108	0	$ 24
Maximum
Income Taxes [Line Items]
Income tax refund maximum from patents	$ 8.0
Investment tax credit carryforward
Income Taxes [Line Items]
Investment tax credits available to reduce Canadian federal income taxes			9,546	10,245
Investment tax credits available to reduce provincial income taxes			4,866	5,337
Research tax credit carryforward
Income Taxes [Line Items]
Scientific research and experimental development expenditures available for indefinite carry-forward			61,493	65,332
Deferred tax assets, operating loss carryforwards, subject to expiration			$ 124,451	$ 71,460
Forecast
Income Taxes [Line Items]
Canadian federal and provincial income tax rate		27.00%

Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Computed taxes (recoveries) at Canadian federal and provincial tax rates	$ (28,270)	$ (127,183)	$ (20,100)
Difference due to change in tax rate on opening deferred taxes	(6,633)	0	0
Permanent and other differences	1,476	(3,598)	769
Change in valuation allowance - other	6,945	17,043	3,675
Difference due to income taxed at foreign rates	(966)	(47,962)	(7,874)
Stock-based compensation	3,128	9,727	7,345
Impairment of goodwill	0	46,971	0
Deferred income tax recovery	$ (24,320)	$ (105,002)	$ (16,185)

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of Deferred Tax Assets [Line Items]
Non-capital loss carryforwards	$ 36,652	$ 24,275
Research and development deductions	16,603	16,986
Book amortization in excess of tax	(650)	451
Share issue costs	456	486
Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes	1,162	410
Tax value in excess of accounting value in lease inducements	173	58
In-process research and development	(16,943)	(41,263)
Upfront license fees	311	536
Other	2,017	1,435
Total deferred tax assets (liabilities)	53,679	17,274
Valuation allowance	(70,622)	(58,537)
Net deferred tax assets (liabilities)	(16,943)	(41,263)
Federal
Components of Deferred Tax Assets [Line Items]
Investment tax credits	9,079	8,630
Provincial
Components of Deferred Tax Assets [Line Items]
Investment tax credits	$ 4,819	$ 5,270

Loan Payable (Details) - USD ($)	12 Months Ended
Loan Payable (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 27, 2016
Debt Instrument [Line Items]
Restricted investment	$ 12,601,000	$ 12,601,000
Restricted investment, term	2 years
LIBOR \| Loans payable \| Promissory note with Wells Fargo
Debt Instrument [Line Items]
Fixed component of interest rate	1.25%
Wells Fargo \| Loans payable \| Promissory note with Wells Fargo
Debt Instrument [Line Items]
Loan payable			$ 12,001,000

Contingencies and Commitments - Minimum Rent and Estimated Operating Cost Commitment, Net Lease Inducements (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Year ended December 31, 2018	$ 1,607
Year ended December 31, 2019	1,243
Year ended December 31, 2020	656
Year ended December 31, 2021	673
Year ended December 31, 2022 and after	3,813
Future minimum rent and estimated operating cost commitment, net of lease inducements	$ 7,992

Contingencies and Commitments - Narrative (Details) $ in Thousands			1 Months Ended			12 Months Ended				53 Months Ended
	Jun. 05, 2016 USD ($) research_funding_period_extensions	Jan. 16, 2015 USD ($)	Nov. 30, 2014 USD ($)	Oct. 31, 2014 USD ($)	Feb. 28, 2014 USD ($) compound_series	Dec. 31, 2017 USD ($)	Dec. 31, 2017 CAD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2004 USD ($)	Mar. 31, 2004 CAD ($)	Dec. 31, 2017 CAD ($)
Contingencies and Commitments [Line Items]
Lease expense						$ 1,653,000		$ 1,341,000	$ 1,158,000
Percent of costs funded by TPC										27.00%	27.00%
Maximum contribution for product										$ 7,179,000	$ 9,330
Cumulative contribution for product						$ 2,951,000	$ 3,702
Royalty guarantees commitments percentage						2.50%	2.50%
Arbutus Inc. \| Enantigen
Contingencies and Commitments [Line Items]
Business combination, high end of payment upon achievement of certain triggering events				$ 21,000,000
Business combination, regulatory, development and sales milestone payments estimated fair value				6,727,000
Arbitration with the University of British Columbia
Contingencies and Commitments [Line Items]
Loss contingency, damages sought for allegedly unpaid royalties		$ 3,500,000
Blumberg and Drexel \| Arbutus Inc.
Contingencies and Commitments [Line Items]
Number of series of compounds \| compound_series					3
License fee			$ 50,000		$ 150,000
Development and regulatory milestones payment per licensed compound series, maximum			$ 1,000,000		3,500,000
Sales performance milestones payment per licensed product, maximum					$ 92,500,000
Blumberg \| Arbutus Inc.
Contingencies and Commitments [Line Items]
Research funding per year under research collaboration and funding agreement	$ 1,100,000			$ 1,000,000
Research funding period				3 years
Research funding period, renewable option	1 year			3 years
Research funding agreement exclusive license upfront payment				$ 100,000
Research funding agreement exclusive license maximum development and regulatory milestone payments				8,100,000
Research funding agreement license maximum commercialization milestone payments				$ 92,500,000
Research funding period, number of renewable options \| research_funding_period_extensions	2
Marqibo
Contingencies and Commitments [Line Items]
Royalty revenue						$ 191,000
Royalty payable						5,000		$ 5,000	$ 6,000
Royalties paid or accrued						22,000
Contractual obligation						$ 2,929,000						$ 3,674

Concentrations of Business Risk - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Risks and Uncertainties [Abstract]
Accounts receivable	$ 402	$ 273
Financial obligations, period to pay	45 days

Concentrations of Business Risk - Net Liquidity of the Company (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Risks and Uncertainties [Abstract]
Cash, cash equivalents and short-term investments	$ 126,352	$ 130,559
Less: Accounts payable and accrued liabilities	(10,646)	(9,910)
Net liquidity	$ 115,706	$ 120,649

- Definition

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

+ References + Details

Concentrations of Business Risk - Foreign Currency Exposure (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Intercompany Foreign Currency Balance [Line Items]
Cash and cash equivalents and short-term investments	$ 126,352	$ 130,559
Accounts receivable	402	273
Accrued revenue	128	128
Accounts payable and accrued liabilities	(10,646)	(9,910)
Foreign currency exposure
Intercompany Foreign Currency Balance [Line Items]
Cash and cash equivalents and short-term investments	25,921	43,094
Accounts receivable	375	289
Accrued revenue	0	128
Accounts payable and accrued liabilities	(1,273)	(3,238)
Exposure to Canadian dollar	$ 25,023	$ 40,273

- Definition

+ References + Details

Supplementary Information (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Trade accounts payable	$ 1,987	$ 3,215
Research and development accruals	4,937	3,131
Professional fee accruals	429	498
Deferred lease inducements	42	350
Payroll accruals	2,893	2,178
Other accrued liabilities	358	538
Accounts payable and accrued liabilities	$ 10,646	$ 9,910

Interim Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 2,534	$ 6,892	$ 1,039	$ 235	$ (195)	$ 774	$ 309	$ 603	$ 10,700	$ 1,491	$ 23,276
Loss from operations	(60,249)	(12,897)	(19,485)	(18,299)	(257,439)	(18,975)	(195,248)	(19,977)	(110,930)	(491,639)	(103,919)
Net loss	$ (36,842)	$ (11,600)	$ (18,255)	$ (18,627)	$ (218,695)	$ (19,595)	$ (130,000)	$ (15,874)	$ (84,413)	$ (384,164)	$ (62,718)
Basic and diluted net loss attributable to shareholders per share (USD per share)	$ (0.67)	$ (0.21)	$ (0.33)	$ (0.34)	$ (4.05)	$ (0.37)	$ (2.47)	$ (0.31)	$ (1.56)	$ (7.24)

Subsequent Events (Details) - USD ($) $ in Thousands				12 Months Ended
Subsequent Events (Details) - USD ($) $ in Thousands	Jan. 12, 2018	Oct. 16, 2017	Oct. 02, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 02, 2018
Subsequent Event [Line Items]
Preferred stock, shares issued				500,000	0
Proceeds from Issuance of Convertible Preferred Stock				$ 48,869	$ 0	$ 0
Issuance of common shares in conjunction with the private offering, net of issuance costs						$ 142,177
Roivant Sciences Ltd
Subsequent Event [Line Items]
Proceeds from Issuance of Convertible Preferred Stock		$ 50,000
Roivant Sciences Ltd \| Subsequent event
Subsequent Event [Line Items]
Preferred stock, shares issued	664,000
Proceeds from Issuance of Convertible Preferred Stock	$ 66,400
Convertible Preferred Stock \| Roivant Sciences Ltd
Subsequent Event [Line Items]
Issuance of common shares in conjunction with the private offering, net of issuance costs			$ 116,400
Convertible Preferred Stock \| Roivant Sciences Ltd \| Subsequent event
Subsequent Event [Line Items]
Issuance of common shares in conjunction with the private offering, net of issuance costs	$ 116,400
Consolidation of HBV Business \| Subsequent event
Subsequent Event [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated, Percent							31.00%
Restructuring and Related Cost, Expected Cost							$ 5,000

Consolidated Statement of Stockholders Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Issuance costs of stock issued	$ 1,131	$ 4,085

Refundable Investment Tax Credits	12 Months Ended
Refundable Investment Tax Credits	Dec. 31, 2017
Government Grants And Refundable Investment Tax Credits [Abstract]
Refundable investment tax credits	Refundable investment tax credits Refundable investment tax credits have been recorded as a reduction in research and development expenses. The Company’s estimated claim for refundable Scientific Research and Experimental Development investment tax credits for the year ended December 31, 2017 is $183,000 (2016 - $145,000).

Refundable Investment Tax Credits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Government Grants And Refundable Investment Tax Credits [Abstract]
Investment Tax Credit	$ 183	$ 145

Property and Equipment (Details)	12 Months Ended
Property and Equipment (Details)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Abstract]
Asset impairment charges	$ 0