Arbitration with the University of British Columbia Arbitration With The University Of British Columbia [Member] Information related to arbitration with the University of British Columbia. Supplemental cash flow information Supplemental Cash Flow Information [Abstract] Accretion of accumulated dividends on Preferred Shares Preferred Stock, Accretion of Redemption Discount Lease liability, non-current Operating Lease, Liability, Noncurrent Fair Value, Measurement Frequency [Domain] Measurement Frequency [Domain] Net loss attributable to common shareholders per share Earnings Per Share, Policy [Policy Text Block] Interest expense Interest Expense Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Net loss Net loss Net loss Net Income (Loss) Attributable to Parent Entity Emerging Growth Company Entity Emerging Growth Company Genevant Genevant Sciences Corporation [Member] Genevant Sciences Corporation [Member] Right of use asset Operating Lease, Right-of-Use Asset Investments in marketable securities, current Investments in marketable short-term securities, Fair Value Debt Securities, Available-for-sale, Current Preferred stock, shares outstanding 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Method Investments Income Statement [Abstract] Amendment Flag Amendment Flag Entity Filer Category Entity Filer Category Other non-current assets Other Assets, Noncurrent Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Investment, Name [Axis] Investment, Name [Axis] Aug 2020 Prospectus Supplement Agreement Aug 2020 Prospectus Supplement Agreement [Member] Aug 2020 Prospectus Supplement Agreement Issuance of common shares pursuant to exercise of options Proceeds from Stock Options Exercised (Decrease) increase in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Related Party Transaction [Axis] Related Party Transaction [Axis] US government money market fund US Government Money Marke tFund [Member] US Government Money Marke tFund Effective annual interest 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Organization, Consolidation and Presentation of Financial Statements [Abstract] Entity File Number Entity File Number Equity Method Investments and Joint Ventures [Abstract] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Statement of Financial Position [Abstract] Enantigen's Selling Shareholders Enantigen's Selling Shareholders [Member] Enantigen's Selling Shareholders Anti-dilutive common shares excluded from calculation of loss per common share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Contingent consideration Fair value of contingent consideration Liability at beginning of the period Liability at end of the period Business Combination, Contingent Consideration, Liability, Noncurrent Fair value measurements Fair Value Measurement, Policy [Policy Text Block] Research and development Research and 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Contingent Consideration [Table Text Block] Assets Assets [Abstract] Related Party Transactions [Abstract] Statement [Line Items] Statement [Line Items] Litigation Case [Axis] Litigation Case [Axis] Non-cash interest expense Non Cash Interest Expense Related To Sale Of Future Royalties Non Cash Interest Expense Related To Sale Of Future Royalties Products and Services [Table] Products and Services [Table] Arbitration settlement, amount awarded to other party Litigation Settlement, Amount Awarded to Other Party Cash equivalents Cash Equivalents [Member] Other Liabilities Disclosure [Line Items] Other Liabilities Disclosure [Line Items] Other Liabilities Disclosure [Line Items] Investments in marketable long-term securities, Fair Value Long-term marketable securities with contractual maturities of more than one year but less than five years Debt Securities, Available-for-sale, Noncurrent Purchase of investments Payments to Acquire Investments Gross proceeds from sale of royalty interest. before advisory fees Gross Proceeds From Royalty Interest Sold Gross Proceeds From Royalty Interest Sold Entity Address, City or Town Entity Address, City or Town Jefferies LLC Jefferies LLC [Member] Jefferies LLC Investments in marketable securities, current Debt Securities, Available-for-sale Disposition of investments Proceeds from Sale, Maturity and Collection of Investments Deficit Retained Earnings [Member] Counterparty Name [Domain] Counterparty Name [Domain] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Alnylam Pharmaceuticals, Inc. Alnylam Pharmaceuticals, Inc [Member] Alnylam Pharmaceuticals, Inc Research and development accruals Accrued Research And Development Research and development accruals Entity Address, State or Province Entity Address, State or Province Other Liabilities Disclosure [Abstract] Contingencies and commitments Commitments and Contingencies Disclosure [Text Block] Loss before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Arbitration settlement interest Litigation Settlement Interest Level 2 Fair Value, Inputs, Level 2 [Member] Entity [Domain] Entity [Domain] Investments in marketable long-term securities, Amortized Cost Debt Securities, Available-for-sale, Amortized Cost, Noncurrent Accounts receivable Increase (Decrease) in Accounts Receivable Liability related to sale of future royalties Net liability related to sale of future royalties - beginning balance Net liability related to sale of future royalties - ending balance Liability Related To Sale Of Future Royalties, Noncurrent Liability Related To Sale Of Future Royalties, Noncurrent Options granted during period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Entity Shell Company Entity Shell Company Local Phone Number Local Phone Number Schedule of stock based compensation expense Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Entity Interactive Data Current Entity Interactive Data Current Issuance of common shares pursuant to the Open Market Sale agreement Proceeds from issuance of shares under the agreement Proceeds from Issuance of Common Stock Total assets Assets Contingencies and Commitments [Table] Contingencies and Commitments [Table] Investment, Name [Domain] Investment, Name [Domain] Number of wholly-owed subsidiaries Wholly Owned Subsidiaries Included in Financial Statements Represents the number of wholly owned subsidiaries included in the reporting of the financial statements. Plan Name [Domain] Plan Name [Domain] Investment commitment period Noncontrolling Interest, Investment Commitment Period Noncontrolling Interest, Investment Commitment Period Basic (in USD per share) Earnings Per Share, Basic Net loss attributable to common shares Net Income (Loss) Available to Common Stockholders, Basic Research and development Research and Development Expense Product and Service [Domain] Product and Service [Domain] Proceeds from sale of stock Proceeds from Issuance of Convertible Preferred Stock Development and regulatory milestones payment per licensed compound series, maximum License Agreement Maximum Development And Regulatory Milestone Payments Per License License Agreement, Maximum Development and Regulatory Milestone Payments Per License Document Type Document Type Royalty guarantees commitments percentage Royalty Guarantees Commitments Percentage Represents the royalty guarantees commitments percentage. Number of royalty entitlements Royalty Entitlements Royalty Entitlements Non-cash royalty revenue Non-Cash Royalty [Member] Non-Cash Royalty Non-cash royalty revenue Liability From Sale Of Future Royalties, Non Cash Royalty Income Liability From Sale Of Future Royalties, Non Cash Royalty Income Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Sub-licensing revenue percentage Sub-licensing revenue Percentage Sub-licensing revenue Percentage Significant accounting policies Significant Accounting Policies [Text Block] Assembly Biosciences, Inc. Assembly Biosciences, Inc. [Member] Assembly Biosciences, Inc. Royalty, interest sold, percentage Royalty, Percentage of Interest Sold Royalty, Percentage of Interest Sold Entity Current Reporting Status Entity Current Reporting Status Measurement Frequency [Axis] Measurement Frequency [Axis] Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Entity Tax Identification Number Entity Tax Identification Number Preferred stock dividend rate as a percent Preferred Stock, Dividend Rate, Percentage Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in USD per share) Earnings Per Share, Diluted Investment Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Payroll accruals Accrued Payroll Current Accrued Payroll Current Weighted average number of common shares Weighted Average Number Of Common Shares [Abstract] Weighted average number of common shares Non-cash royalty revenue Non-cash royalty revenue Non Cash Royalty Revenue Related To Sale Of Future Royalties Non Cash Royalty Revenue Related To Sale Of Future Royalties Plan Name [Axis] Plan Name [Axis] Assets Assets, Fair Value Disclosure [Abstract] Comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Total Assets, Fair Value Disclosure Level 1 Fair Value, Inputs, Level 1 [Member] INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Unrealized foreign exchange losses (gains) Foreign Currency Transaction Gain (Loss), Unrealized Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Document Transition Report Document Transition Report Related Party Transaction [Line Items] Related Party Transaction [Line Items] Items applicable to preferred shares: Preferred Stock Dividends and Other Adjustments [Abstract] Equity investment loss Income (Loss) from Equity Method Investments Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] US government agency bonds US Government Agency Bonds [Member] US Government Agency Bonds [Member] Total liabilities and stockholders’ equity Liabilities and Equity Future royalty payments Royalty Payable Represents the royalty payable. Other accrued liabilities Other Accrued Liabilities, Current Costs related to collaboration Other Cost and Expense, Operating Investments, Debt and Equity Securities [Abstract] Fair value measurements Fair Value Disclosures [Text Block] Site consolidation Restructuring Charges Depreciation Depreciation, Depletion and Amortization Additional paid-in capital Additional Paid in Capital Arbutus Plans Arbutus Plans [Member] Arbutus Plans [Member] Assets and liabilities measured at fair value on a recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Liabilities and stockholders’ equity Liabilities and Equity [Abstract] Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Accounts payable and accrued liabilities Total accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities, Current Convertible Preferred Stock Convertible Preferred Stock [Member] Marketable Securities [Table] Marketable Securities [Table] Common shares, shares outstanding (in shares) Common Stock, Shares, Outstanding Income from services (less than) Related Party Transaction, Other Revenues from Transactions with Related Party Long-term investments Long-term Investments Financial Instruments [Domain] Financial Instruments [Domain] Operating expenses Operating Expenses [Abstract] Ownership interest in equity method investment (as a percentage) Equity Method Investment, Ownership Percentage Investments in marketable short-term securities, Amortized Cost Debt Securities, Available-for-sale, Amortized Cost, Current Revenue Revenues [Abstract] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Issuance of common shares pursuant to exercise of options Stock Issued During Period, Value, Stock Options Exercised Minimum Minimum [Member] Change in fair value of contingent consideration Increase (decrease) in fair value of contingent consideration Increase (decrease) in fair value of liability Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Effect of foreign exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Liability classified stock options Employee Stock Option, Liability Classified [Member] Employee Stock Option, Liability Classified [Member] Income Statement Location [Domain] Income Statement Location [Domain] Gross Unrealized Gain Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Short-term investments Investments, Fair Value Disclosure Trading Symbol Trading Symbol Loss contingency, damages sought for allegedly unpaid royalties Loss Contingency, Damages Sought, Value Property and equipment, net of accumulated depreciation of $(8,499) (December 31, 2020: $7,621) Property, Plant and Equipment, Net Total operating expenses Operating Expenses Entitlement of royalties to be received Royalty Interest Sold, Maximum Royalties For Buyer Royalty Interest Sold, Maximum Royalties For Buyer Preferred shares dividends accrued Dividends, Preferred Stock, Cash Current liabilities: Liabilities, Current [Abstract] Issuance of common shares pursuant to the Open Market Sale Agreement Issuance of common shares pursuant to the agreement Stock Issued During Period, Value, New Issues General and administrative General and Administrative Expense Acuitas Therapeutics, Inc. Acuitas Therapeutics Inc. [Member] Acuitas Therapeutics Inc. Loss per share Earnings Per Share [Abstract] Level 3 Fair Value, Inputs, Level 3 [Member] Accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities Disclosure [Text Block] Related Party Transaction [Domain] Related Party Transaction [Domain] Accounting Policies [Abstract] Document Quarterly Report Document Quarterly Report Revenue Revenues Issuance of common shares pursuant to the Open Market Sales Agreement (in shares) Stock Issued During Period, Shares, New Issues Number of segments Number of Reportable Segments Professional fee accruals Accrued Professional Fees, Current Changes in fair value of liability option Changes In Fair Value of Liability Option [Table Text Block] Changes In Fair Value of Liability Option [Table Text Block] Foreign exchange (loss) gain Foreign Currency Transaction Gain (Loss), before Tax Common shares, Authorized - unlimited number without par value, Issued and outstanding: 97,700,016 (December 31, 2020 - 89,678,722) Common Stock, 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[Table] Schedule of Related Party Transactions, by Related Party [Table] Allocated share-based compensation expense Share-based Payment Arrangement, Expense Transaction costs on sale of royalties Transaction Costs Related To Sale Of Future Royalties Transaction Costs Related To Sale Of Future Royalties Aggregate sale price of common shares under agreement Common Stock, Value, Subscriptions Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Non-cash interest expense Liability From Sale Of Future Royalties, Non Cash Expense Liability From Sale Of Future Royalties, Non Cash Expense Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Document Fiscal Period Focus Document Fiscal Period Focus Collaborations and licenses Collaboration And Contracts [Member] Collaboration And Contracts [Member] Net accretion and amortization of investments in marketable securities Accretion (Amortization) of Discounts and Premiums, Investments Development and regulatory milestones payment per royalty, maximum License Agreement Maximum Development And Regulatory Milestone Payments Per Royalty License Agreement Maximum Development And Regulatory Royalty Payment per Royalty Counterparty Name [Axis] Counterparty Name [Axis] Document Period End Date Document Period End Date Payables and Accruals [Abstract] Investments in marketable securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Fair Value, Liabilities Measured on Recurring Basis [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis [Roll Forward] Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Beginning balance (in shares) Ending balance (in shares) Shares, Issued Class of Stock [Axis] Class of Stock [Axis] Contingencies and Commitments [Line Items] Contingencies and Commitments [Line Items] Number of shares issued under agreement (in sales) Sale of Stock, Number of Shares Issued in Transaction Entity Registrant Name Entity Registrant Name Realized gains or losses Debt Securities, Realized Gain (Loss) Current assets: Assets, Current [Abstract] Research and Development Arrangement, Contract to Perform for Others [Line Items] Research and Development Arrangement, Contract to Perform for Others [Line Items] Increase (decrease) in fair value of liability Increase (Decrease) in Fair Value of Liability Classified Options Increase (Decrease) in Fair Value of Liability Classified Options Entity Central Index Key Entity Central Index Key Security Exchange Name Security Exchange Name Cash and cash equivalents Cash and cash equivalents, Fair Value Cash and Cash Equivalents, Fair Value Disclosure Schedule of accounts payable and accrued liabilities Schedule of Accounts Payable and 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Bonds [Member] US Government Bonds [Member] Current Fiscal Year End Date Current Fiscal Year End Date Stockholders’ equity Stockholders' Equity Note Disclosure [Text Block] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Statement of Cash Flows [Abstract] Liability-classified options Employee Stock Options, Liability Classified, Outstanding Employee Stock Options, Liability Classified, Outstanding Class of Stock [Line Items] Class of Stock [Line Items] Schedule of activity related to the net liability from inception of the Agreement Liabilities Related To Sale Of Future Royalties Roll Forward [Table Text Block] Liabilities Related To Sale Of Future Royalties Roll Forward Common Shares Common Stock [Member] Interest income Investment Income, Interest Net cash (used) provided by investing activities Net Cash Provided by (Used in) Investing Activities Net change in operating items: Increase (Decrease) in Operating Capital [Abstract] Issuance of common shares pursuant to ESPP Stock Issued During Period, Value, Employee Stock Purchase Plan Accumulated depreciation of property and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Loss from operations Operating Income (Loss) OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] General and administrative General and Administrative Expense [Member] Principles of consolidation Consolidation, Policy [Policy Text Block] Annual royalty revenue Royalty Interest Sold, Percentage Of Sales, Annual Revenue Threshold Of Highest Tier Royalty Interest Sold, Percentage Of Sales, Annual Revenue Threshold Of Highest Tier Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Liability-classified options Liability at beginning of the period Liability at end of the period Employee Stock Options, Liability Classified, Outstanding, Fair Value Disclosure Employee Stock Options, Liability Classified, Outstanding, Fair Value Disclosure Lease liability, current Operating Lease, Liability, Current Gross Unrealized Loss Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Collaborations, contracts and licensing agreements Collaborative Arrangement Disclosure [Text Block] Total current liabilities Liabilities, Current Class of Stock [Domain] Class of Stock [Domain] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense Additional Paid-In Capital Additional Paid-in Capital [Member] Cash and cash equivalents Cash and cash equivalents, Amortized Cost Cash and Cash Equivalents, at Carrying Value Maximum ownership percentage by noncontrolling owners Noncontrolling Interest, Maximum Ownership Percentage by Noncontrolling Owners Noncontrolling Interest, Maximum Ownership Percentage by Noncontrolling Owners OMERS OMERS [Member] OMERS Depreciation Depreciation 2021 Prospectus Supplement Agreement Mar 2021 Prospectus Supplement Agreement [Member] Prospectus Supplement - Open Market Sale Agreement Mar 2021 Trade accounts payable Accounts Payable, Trade, Current Entity Address, Postal Zip Code Entity Address, Postal Zip Code Arbitration settlement payment Payments for Legal Settlements Title of 12(b) Security Title of 12(b) Security Marketable securities Marketable Securities [Table Text Block] Issuance of common shares pursuant to ESPP Proceeds from Stock Plans Other liabilities Increase (Decrease) in Other Operating Liabilities Statement [Table] Statement [Table] Recent accounting pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Acquisition of property and equipment Payments to Acquire Property, Plant, and Equipment Preferred shares, Authorized; unlimited number without par value; Issued and outstanding: 1,164,000 (December 31, 2020: 1,164,000) Preferred Stock, Including Additional Paid in Capital, Net of Discount Maximum Maximum [Member] Range [Axis] Statistical Measurement [Axis] Liability Related To Sale Of Future Royalties [Roll Forward] Liability Related To Sale Of Future Royalties [Roll Forward] Liability Related To Sale Of Future Royalties [Roll Forward] Sale of future royalties Liabilities Related To Sale Of Future Royalties [Text Block] Liabilities Related To Sale Of Future Royalties Summary of collaborations Collaborative Arrangement and Arrangement Other than Collaborative [Table Text Block] Total liabilities Liabilities 2019 Amended Sale Agreement 2019 Amended Sale Agreement [Member] 2019 Amended Sale Agreement Legal Entity [Axis] Legal Entity [Axis] Cover [Abstract] Stockholders' Equity Note [Abstract] Premium on closing stock price (as a percent) Premium on Closing Stock Price Premium on Closing Stock Price Award Type [Axis] Award Type [Axis] Convertible Preferred Shares Preferred Stock [Member] Weighted average exercise price (in USD per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Arbutus Inc. Arbutus Inc. [Member] Arbutus Inc. [Member] Total stockholders’ equity Beginning balance Ending balance Stockholders' Equity Attributable to Parent Roivant Sciences Ltd Roivant Sciences Ltd [Member] Roivant Sciences Ltd [Member] Change in fair value of contingent consideration Increase (Decrease) In Fair Value Of Contingent Consideration Liability Increase (Decrease) In Fair Value Of Contingent Consideration Liability Common shares, shares issued (in shares) Common Stock, Shares, Issued Revenue from collaborations and licenses License [Member] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Accounts payable and accrued liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Nature of business and future operations Nature of Operations [Text Block] Investment in Genevant Equity Method Investments and Joint Ventures Disclosure [Text Block] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Related party transactions Related Party Transactions Disclosure [Text Block] Ownership percentage by noncontrolling owners after conversion Noncontrolling Interest, Ownership Percentage By Noncontrolling Owners After Conversion Noncontrolling Interest, Ownership Percentage By Noncontrolling Owners After Conversion Stockholders’ equity Stockholders' Equity Attributable to Parent [Abstract] Non-cash items: Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]