Document Type Document Type 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. Fair Value Disclosures [Abstract] Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Options granted during period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Contingencies and commitments Commitments and Contingencies Disclosure [Text Block] Net accretion and amortization of investments in marketable securities Accretion (Amortization) of Discounts and Premiums, Investments Related Party [Axis] Related Party [Axis] Unrealized gain on available-for-sale securities Debt Securities, Available-for-sale, Unrealized Gain (Loss) Accounts payable and accrued liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Payables and Accruals [Abstract] Genevant Genevant Sciences Corporation [Member] Genevant Sciences Corporation [Member] Fair Value Investments in marketable securities, current Debt Securities, Available-for-sale Investments in marketable securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Equity Components [Axis] Equity Components [Axis] SEC Filing Prospectus Supplement [Member] August 2020 Prospectus Supplement [Member] August 2020 Prospectus Supplement Other milestone and royalty payments Other Milestone and Royalty Payments [Member] Other Milestone and Royalty Payments [Member] Minimum Minimum [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Lease liability, current Operating Lease, Liability, Current Range [Domain] Statistical Measurement [Domain] Liabilities and stockholders’ equity Liabilities and Equity [Abstract] Schedule of changes in fair value of contingent consideration Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table Text Block] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Equity Method Investments and Joint Ventures [Abstract] Entity Interactive Data Current Entity Interactive Data Current Convertible Preferred Shares Preferred Stock [Member] Revenue Revenues [Abstract] Security Exchange Name Security Exchange Name Fair value measurements Fair Value Disclosures [Text Block] OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] Stockholders’ equity Stockholders' Equity Note Disclosure [Text Block] Aug 2020 Prospectus Supplement Agreement Aug 2020 Prospectus Supplement Agreement [Member] Aug 2020 Prospectus Supplement Agreement Loss from operations Operating Income (Loss) US government money market fund US Government Money Marke tFund [Member] US Government Money Marke tFund Effective annual interest rate on royalty liability Effective Annual Interest Rate Of Royalty Liability Effective Annual Interest Rate Of Royalty Liability Total current liabilities Liabilities, Current Arbitration settlement, amount awarded to other party Litigation Settlement, Amount Awarded to Other Party Entity Registrant Name Entity Registrant Name Statement of Stockholders' Equity [Abstract] Assets Assets, Fair Value Disclosure [Abstract] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Other liabilities Increase (Decrease) in Other Operating Liabilities Professional fee accruals Accrued Professional Fees, Current Research and development services Research And Development Services [Member] Research And Development Services [Member] Costs related to collaboration Other Cost and Expense, Operating Certain fair value adjustments to liability stock option awards Adjustments to Additional Paid in Capital, Certain Fair Value Adjustments to Liability Stock Option Awards Adjustments to Additional Paid in Capital, Certain Fair Value Adjustments to Liability Stock Option Awards Assets Assets [Abstract] Investment, Name [Axis] Investment, Name [Axis] Accounting Policies [Abstract] Number of segments Number of Reportable Segments 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 Entity Address, State or Province Entity Address, State or Province Issuance of common shares pursuant to ESPP Proceeds from Stock Plans Enantigen's Selling Shareholders Enantigen's Selling Shareholders [Member] Enantigen's Selling Shareholders Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities Disclosure [Text Block] Research and development Research and Development Expense [Member] Purchase of investments Payments to Acquire Other Investments Deficit Retained Earnings (Accumulated Deficit) Right of use asset Operating Lease, Right-of-Use Asset Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Accounts receivable Accounts Receivable, after Allowance for Credit Loss, Current Preferred shares dividends accrued Dividends, Preferred Stock, Cash Arbitration settlement payment Payments for Legal Settlements Gross Unrealized Loss Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax 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] Sale of Stock [Axis] Sale of Stock [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Non-cash interest expense Non Cash Interest Expense Related To Sale Of Future Royalties Non Cash Interest Expense Related To Sale Of Future Royalties Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Total operating expenses Operating Expenses Other Liabilities Disclosure [Line Items] Other Liabilities Disclosure [Line Items] Other Liabilities Disclosure [Line Items] Document Transition Report Document Transition Report Gross proceeds from sale of royalty interest. before advisory fees Gross Proceeds From Royalty Interest Sold Gross Proceeds From Royalty Interest Sold Realized gains or losses Debt Securities, Realized Gain (Loss) Jefferies LLC Jefferies LLC [Member] Jefferies LLC Stock-based compensation APIC, Share-based Payment Arrangement, Increase for Cost Recognition Level 2 Fair Value, Inputs, Level 2 [Member] 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 Alnylam Pharmaceuticals, Inc. Alnylam Pharmaceuticals, Inc [Member] Alnylam Pharmaceuticals, Inc Research and development accruals Accrued Research And Development Research and development accruals Document Quarterly Report Document Quarterly Report Liabilities Liabilities, Fair Value Disclosure [Abstract] Fair Value, Measurement Frequency [Domain] Measurement Frequency [Domain] General and administrative General and Administrative Expense [Member] Share price (in USD per share) Share Price Total Assets, Fair Value Disclosure Business Acquisition [Axis] Business Acquisition [Axis] Trade accounts payable Accounts Payable, Trade, Current 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 Statement [Line Items] Statement [Line Items] 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 Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Class of Stock [Domain] Class of Stock [Domain] Litigation Case [Domain] Litigation Case [Domain] Basic (in USD per share) Earnings Per Share, Basic Schedule of Research and Development Arrangement, Contract to Perform for Others [Table] Schedule of Research and Development Arrangement, Contract to Perform for Others [Table] Entity File Number Entity File Number Schedule of accounts payable and accrued liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] 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 Statement [Table] Statement [Table] Contingencies and Commitments [Table] Contingencies and Commitments [Table] Range [Axis] Statistical Measurement [Axis] 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. Investment commitment period Noncontrolling Interest, Investment Commitment Period Noncontrolling Interest, Investment Commitment Period Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Arbitration settlement interest Litigation Settlement Interest Allocated share-based compensation expense Share-based Payment Arrangement, Expense 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 Products and Services [Table] Products and Services [Table] Royalty guarantees commitments percentage Royalty Guarantees Commitments Percentage Represents the royalty guarantees commitments percentage. Issuance of common shares pursuant to ESPP Stock Issued During Period, Value, Employee Stock Purchase Plan Counterparty Name [Axis] Counterparty Name [Axis] Common shares, Authorized - unlimited number without par value, Issued and outstanding: 96,245,371 (December 31, 2020 - 89,678,722) Common Stock, Value, Issued 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 Entity Small Business Entity Small Business Document Fiscal Year Focus Document Fiscal Year Focus Principles of consolidation Consolidation, Policy [Policy Text Block] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Sub-licensing revenue percentage Sub-licensing revenue Percentage Sub-licensing revenue Percentage Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Number of shares issued under agreement (in sales) Sale of Stock, Number of Shares Issued in Transaction 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 Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] 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 Related Party Transaction [Axis] Related Party Transaction [Axis] Other Liabilities Disclosure [Abstract] Amendment Flag Amendment Flag Net loss attributable to common shareholders per share Earnings Per Share, Policy [Policy Text Block] US treasury bills US Treasury Bill Securities [Member] Collaborations, contracts and licensing agreements Collaborative Arrangement Disclosure [Text Block] INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Common shares, shares issued (in shares) Common Stock, Shares, Issued Cash and cash equivalents Cash and cash equivalents, Amortized Cost Cash and Cash Equivalents, at Carrying Value Other accrued liabilities Other Accrued Liabilities, Current Fair value measurements Fair Value Measurement, Policy [Policy Text Block] 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 Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Enantigen Enantigen [Member] Enantigen Entity Central Index Key Entity Central Index Key Related Party [Domain] Related Party [Domain] Measurement Frequency [Axis] Measurement Frequency [Axis] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Accounts receivable Increase (Decrease) in Accounts Receivable Investments in marketable securities, current Debt Securities, Available-for-sale, Current Financial Instruments [Domain] Financial Instruments [Domain] Items applicable to preferred shares: Preferred Stock Dividends and Other Adjustments [Abstract] Total stockholders’ equity Beginning balance Ending balance Stockholders' Equity Attributable to Parent Nature of business and future operations Nature of Operations [Text Block] Total liabilities and stockholders’ equity Liabilities and Equity US government agency bonds US Government Agency Bonds [Member] US Government Agency Bonds [Member] Future royalty payments Royalty Payable Represents the royalty payable. Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Address, City or Town Entity Address, City or Town Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Research and Development Arrangement, Contract to Perform for Others [Line Items] Research and Development Arrangement, Contract to Perform for Others [Line Items] Accounts payable and accrued liabilities Total accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities, Current General and administrative General and Administrative Expense Financial Instrument [Axis] Financial Instrument [Axis] Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Anti-dilutive common shares excluded from calculation of loss per common share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Proceeds from Sale, Maturity and Collection of Investments Proceeds from Sale, Maturity and Collection of Investments Arbutus Plans Arbutus Plans [Member] Arbutus Plans [Member] Gross Unrealized Gain Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Statement of Cash Flows [Abstract] Marketable securities Marketable Securities [Table Text Block] Equity Component [Domain] Equity Component [Domain] Cash, cash equivalents and investments in marketable securities Cash, Cash Equivalents, and Short-term Investments Income Statement Location [Axis] Income Statement Location [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Income Statement Location [Domain] Income Statement Location [Domain] FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Property and equipment, net of accumulated depreciation of $8,063 (December 31, 2020: $7,621) Property, Plant and Equipment, Net Entity Tax Identification Number Entity Tax Identification Number Revenue recognition Revenue from Contract with Customer [Policy Text Block] Stockholders' Equity Note [Abstract] Net loss Net loss Net loss Net Income (Loss) Attributable to Parent Net change in operating items: Increase (Decrease) in Operating Capital [Abstract] Other non-current assets Other Assets, Noncurrent Plan Name [Axis] Plan Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Investment in Genevant Equity Method Investments and Joint Ventures Disclosure [Text Block] Unrealized gain on available-for-sale securities Other Comprehensive Income (Loss), Net of Tax 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 Cash and cash equivalents Cash and cash equivalents, Fair Value Cash and Cash Equivalents, Fair Value Disclosure Liability classified stock options Employee Stock Option, Liability Classified [Member] Employee Stock Option, Liability Classified [Member] Total assets Assets Related party transactions Related Party Transactions Disclosure [Text Block] Total current assets Assets, Current Current Fiscal Year End Date Current Fiscal Year End Date Operating expenses Operating Expenses [Abstract] Loss per share Earnings Per Share [Abstract] Site consolidation Restructuring Charges Title of 12(b) Security Title of 12(b) Security Unrealized foreign exchange losses (gains) Foreign Currency Transaction Gain (Loss), Unrealized Entitlement of royalties to be received Royalty Interest Sold, Maximum Royalties For Buyer Royalty Interest Sold, Maximum Royalties For Buyer Investments, Debt and Equity Securities [Abstract] Stockholders’ equity Stockholders' Equity Attributable to Parent [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Acuitas Therapeutics, Inc. Acuitas Therapeutics Inc. [Member] Acuitas Therapeutics Inc. Open Market Sales Agreement Open Market Sales Agreement [Member] Open Market Sales Agreement Interest expense Interest Expense Depreciation Depreciation, Depletion and Amortization Product and Service [Axis] Product and Service [Axis] Total liabilities Liabilities Supplemental cash flow information Supplemental Cash Flow Information [Abstract] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Loss contingency, damages sought for allegedly unpaid royalties Loss Contingency, Damages Sought, Value Issuance of common shares pursuant to ESPP (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans 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] Entity Filer Category Entity Filer Category Schedule of stock based compensation expense Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Common Shares Common Stock [Member] Number of products Number Of Products Number Of Products Product and Service [Domain] Product and Service [Domain] 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 Summary of collaborations Collaborative Arrangement and Arrangement Other than Collaborative [Table Text Block] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Fair value of liability-classified options exercised in the period Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Fair Value Commitments and Contingencies Disclosure [Abstract] Net loss attributable to common shares Net Income (Loss) Available to Common Stockholders, Basic Number of common shares to be issued upon conversion of convertible preferred stock Convertible Preferred Stock, Shares Of Common Stock Issued upon Conversion Convertible Preferred Stock, Shares Of Common Stock Issued upon Conversion Level 1 Fair Value, Inputs, Level 1 [Member] Transaction costs on sale of royalties Transaction Costs Related To Sale Of Future Royalties Transaction Costs Related To Sale Of Future Royalties Non-cash interest expense Liability From Sale Of Future Royalties, Non Cash Expense Liability From Sale Of Future Royalties, Non Cash Expense Preferred stock dividend rate as a percent Preferred Stock, Dividend Rate, Percentage Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Issuance of common shares pursuant to the Open Market Sales Agreement (in shares) Stock Issued During Period, Shares, New Issues Collaborations and licenses Collaboration And Contracts [Member] Collaboration And Contracts [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Dividend accretion of convertible preferred shares Preferred Stock Dividends and Other Adjustments 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 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] Accumulated of property, plant, and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Class of Stock [Line Items] Class of Stock [Line Items] Contingencies and Commitments [Line Items] Contingencies and Commitments [Line Items] Beginning balance (in shares) Ending balance (in shares) Shares, Issued Issuance of common shares pursuant to exercise of options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Litigation Case [Axis] Litigation Case [Axis] Related Party Transactions [Abstract] Increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Revenue from Contract with Customer [Abstract] Total other loss Nonoperating Income (Expense) 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 Equity investment Equity Method Investments Common shares, shares outstanding (in shares) Common Stock, Shares, Outstanding Basis of presentation Basis of Accounting, Policy [Policy Text Block] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Loss before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Investment Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Non-cash items: Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Research and development Research and Development Expense Cash equivalents Cash Equivalents [Member] AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Including Noncontrolling Interest AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Including Noncontrolling Interest [Member] Sale of Stock [Domain] Sale of Stock [Domain] Plan Name [Domain] Plan Name [Domain] Issuance of common shares pursuant to exercise of options Proceeds from Stock Options Exercised Aug 2020 Prospectus Supplement Agreement 2020 Amended Sale Agreement [Member] 2020 Amended Sale Agreement Ownership interest in equity method investment (as a percentage) Equity Method Investment, Ownership Percentage US government bonds US Government Bonds [Member] US Government Bonds [Member] Aggregate sale price of common shares under agreement Common Stock, Value, Subscriptions Proceeds from sale of stock Proceeds from Issuance of Convertible Preferred Stock Additional paid-in capital Additional Paid in Capital Revenue Revenues Class of Stock [Axis] Class of Stock [Axis] Foreign exchange gain (loss) Foreign Currency Transaction Gain (Loss), before Tax Liability-classified options Employee Stock Options, Liability Classified, Outstanding Employee Stock Options, Liability Classified, Outstanding Income Statement [Abstract] Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] 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 Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Lease liability, non-current Operating Lease, Liability, Noncurrent Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Diluted (in USD per share) Earnings Per Share, Diluted Local Phone Number Local Phone Number 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 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 Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Current assets: Assets, Current [Abstract] Disposition of investments Proceeds from Sale of Restricted Investments Interest income Investment Income, Interest 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 Entity Address, Address Line One Entity Address, Address Line One Short-term investments Investments, Fair Value Disclosure 2021 Prospectus Supplement Agreement Mar 2021 Prospectus Supplement Agreement [Member] Prospectus Supplement - Open Market Sale Agreement Mar 2021 Related Party Transaction [Domain] Related Party Transaction [Domain] Entity Emerging Growth Company Entity Emerging Growth Company Issuance of common shares pursuant to exercise of options Stock Issued During Period, Value, Stock Options Exercised Convertible Preferred Stock Convertible Preferred Stock [Member] Comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Income from services (less than) Related Party Transaction, Other Revenues from Transactions with Related Party Preferred stated value (in USD per share) Preferred Stock, Par or Stated Value Per Share Revenue from collaborations and licenses License [Member] Award Type [Axis] Award Type [Axis] Legal Entity [Axis] Legal Entity [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Acquisition of property and equipment Payments to Acquire Property, Plant, and Equipment City Area Code City Area Code Maximum Maximum [Member] Document Period End Date Document Period End Date Deficit Retained Earnings [Member] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding 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] Significant accounting policies Significant Accounting Policies [Text Block] Net cash provided (used) by investing activities Net Cash Provided by (Used in) Investing Activities Payments to Acquire Investments Payments to Acquire Investments Equity investment loss Income (Loss) from Equity Method Investments Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] 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 2019 Amended Sale Agreement [Member] 2019 Amended Sale Agreement [Member] 2019 Amended Sale Agreement Equity Award [Domain] Award Type [Domain] Premium on closing stock price (as a percent) Premium on Closing Stock Price Premium on Closing Stock Price Trading Symbol Trading Symbol Arbutus Inc. Arbutus Inc. [Member] Arbutus Inc. [Member] Roivant Sciences Ltd Roivant Sciences Ltd [Member] Roivant Sciences Ltd [Member] Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense 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 Entity [Domain] Entity [Domain] Cover [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Current liabilities: Liabilities, Current [Abstract] Entity Shell Company Entity Shell Company Recurring Fair Value, Recurring [Member] Equity Method Investee Equity Method Investee [Member] Segment information Segment Reporting, Policy [Policy 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 Accretion of accumulated dividends on Preferred Shares Preferred Stock, Accretion of Redemption Discount Recent accounting pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Statement of Financial Position [Abstract]