Entity Address, City or Town Entity Address City Or Town Terminated Employees Employee Severance [Member] Level 1 Fair Value Inputs Level1 [Member] Schedule of Other Accrued Expenses Schedule Of Accrued Liabilities Table [Text Block] Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs Stock Issued During Period Value New Issues Cash flows from financing activities Net Cash Provided By Used In Financing Activities [Abstract] Expected dividend yield Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate Amendment Flag Amendment Flag Total fair value of awards vested and settled Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value Shares reserved for issuance (in shares) Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized Subsequent Event Type Subsequent Event Type [Domain] Executive Officer Chief Executive Officer Executive Officer [Member] Operating lease right-of-use (ROU) assets Operating Lease Right Of Use Asset Short-term marketable securities Short Term Investments [Abstract] Document Quarterly Report Document Quarterly Report Gross Unrealized Gain Cash Equivalents At Carrying Value And Available For Sale Debt Securities Gross Unrealized Gain Cash equivalents at carrying value and available for sale debt securities gross unrealized gain. Proceeds from sale of marketable securities Proceeds From Sale Of Available For Sale Securities Debt Net Loss per Share Earnings Per Share Policy [Text Block] Cash and Cash Equivalents Restricted Cash And Cash Equivalents Cash And Cash Equivalents [Member] Statement [Table] Statement [Table] Operating lease liabilities - long-term Operating Lease Liability Noncurrent Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares) Stock Issued During Period Shares Employee Stock Purchase Plans Operating segments (in segments) Number Of Operating Segments Preferred Stock, Shares Outstanding, Ending Balance Preferred Stock, Shares Outstanding, Beginning Balance Preferred stock, shares outstanding Preferred Stock Shares Outstanding Restructuring charges Costs incurred Restructuring Charges Restructuring Charges, Total Milestones and Research Agreements Milestones And Research Agreements [Text Block] Milestones and Research Agreements Non-Executive Officers Non Executive Officers [Member] Non-executive officers. Grant date fair value non options Beginning of period Ending of period Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Vested Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value Wind-down of Microbiome Program Wind Down Of Microbiome Program [Member] Wind- own of microbiome program. Employee-related Liabilities, Current, Total Accrued compensation Employee Related Liabilities Current Options to purchase common stock Options Employee Stock Option [Member] Total liabilities and stockholders' equity Liabilities And Stockholders Equity Plan Name Plan Name [Domain] Total intrinsic value of awards vested and settled Sharebased Compensation Arrangement By Sharebased Payment Award Equity Instruments Other Than Options Aggregate Intrinsic Value Vested Gross Unrealized Loss, Long-term marketable securities Available For Sale Debt Securities Accumulated Gross Unrealized Loss before Tax Noncurrent Available for sale debt securities accumulated gross unrealized loss before tax noncurrent. Denominator: Weighted Average Number Of Shares Outstanding [Abstract] Percentage of workforce reduced Restructuring and Related Cost, Number of Positions Eliminated, Period Percent Entity Incorporation, State or Country Code Entity Incorporation State Country Code Income Statement [Abstract] Outside of United States Non Us [Member] Subsidiary Or Equity Method Investee Sale Of Stock By Subsidiary Or Equity Investee [Table] Subsidiary Or Equity Method Investee Sale Of Stock By Subsidiary Or Equity Investee [Table] Nature of Business Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Sale of Stock Sale Of Stock Name Of Transaction [Domain] Total current liabilities Liabilities Current Issuance of common stock under Employee Stock Purchase Plan (ESPP) Stock Issued During Period Value Employee Stock Purchase Plan Recurring Fair Value Measurements Recurring [Member] Other Accrued Expenses Accounts Payable And Accrued Liabilities Disclosure [Text Block] Income Taxes Income Tax Policy [Text Block] Gross Unrealized Loss Cash And Cash Equivalent Gross Unrealized Loss Cash and cash equivalent gross unrealized loss. Deferred revenue Increase (Decrease) in Contract with Customer, Liability Schedule of Restructuring Charges Schedule Of Restructuring Charges [Table TextBlock] Schedule of restructuring charges. Collaboration Agreement [Abstract] Collaboration Agreement Preferred stock, shares authorized Preferred Stock Shares Authorized Other Assets Other Noncurrent Assets [Member] Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] Entity Small Business Entity Small Business Collaborative Arrangement and Arrangement Other than Collaborative Type Of Arrangement [Axis] Success Based Milestones Payment Success Based Milestones Payment Success-based milestones payment. Investments Investment Type Categorization [Member] Restructuring and Related Activities [Abstract] Total current assets Assets Current Weighted average common shares outstanding - basic Weighted Average Number of Shares Outstanding, Basic, Total Weighted average common shares outstanding, basic Weighted Average Number Of Shares Outstanding Basic City Area Code City Area Code Option, Outstanding Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value Option, Forfeited Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Total liabilities Liabilities Document Period End Date Document Period End Date Asset-backed securities Asset Backed Securities [Member] Weighted-average grant-date fair value of options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Market-based Vesting Conditions Share-Based Payment Arrangement, Tranche One [Member] Deferred revenue Contract With Customer Liability Noncurrent Statistical Measurement Range [Axis] Subsequent Event [Line Items] Subsequent Event [Line Items] Interest and other income, net Interest Income Other Total assets Assets Earnings Per Share, Diluted, Total Net loss per share - diluted Net loss per share, diluted Earnings Per Share Diluted Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Entity Address, Postal Zip Code Entity Address Postal Zip Code Collaboration revenue Revenue from Contract with Customer, Including Assessed Tax Document Fiscal Period Focus Document Fiscal Period Focus Accounts receivable from collaboration Increase Decrease In Accounts Receivable Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued or outstanding Preferred Stock Value APIC, Share-Based Payment Arrangement, Increase for Cost Recognition, Total Stock-based compensation Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Option Indexed to Issuer's Equity, Type Option Indexed To Issuers Equity Type [Axis] Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Fair Value Measurements and Investments in Marketable Securities Fair Value Measurements And Investments In Marketable Securities [Text Block] Fair value measurements and investments in marketable securities. Statement Of Financial Position [Abstract] Entity File Number Entity File Number Statement Of Cash Flows [Abstract] Geographical Segment Geographical [Domain] Statistical Measurement Range [Member] Fair Value Cash Equivalents At Carrying Value And Available For Sale Debt Securities Estimated Fair Value Cash equivalents at carrying value and available for sale debt securities estimated fair value. Statement Of Stockholders Equity [Abstract] Sale of Stock Subsidiary Sale Of Stock [Axis] Other accrued expenses Increase Decrease In Other Accrued Liabilities Subsequent Events [Abstract] Other comprehensive loss Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent [Abstract] Options Vested and Exercisable, Weighted Average Remaining Contractual Term (Years) Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 Proceeds from the issuance of common stock under ATM equity offering program, net of issuance costs Proceeds From Issuance Of Common Stock Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Preferred stock, par value Preferred Stock Par Or Stated Value Per Share FDA approved products (in products) Number Of Approved Products Represents the number of approved products. Available for sale securities maturity term Available For Sale Securities Maturity Term The contractual term to maturity of short-term marketable securities and long-term marketable securities held by the Company. Subsequent Events Subsequent Events [Text Block] Weighted average common shares outstanding - diluted Weighted Average Number of Shares Outstanding, Diluted, Total Weighted average common shares outstanding, diluted Weighted Average Number Of Diluted Shares Outstanding Gross Unrealized Gain, Short-term marketable securities Available for Sale Debt Securities Accumulated Gross Unrealized Gain before Tax Current Available for sale debt securities accumulated gross unrealized gain before tax current. Cash equivalents Cash Equivalents [Member] Unrecognized stock-based compensation expense Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Share Based Awards Other Than Options U.S and foreign corporate debt securities Corporate Debt Securities [Member] General and Administrative General and Administrative Expenses General And Administrative Expense [Member] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others Type [Domain] U.S. and foreign commercial paper Commercial Paper [Member] Current Fiscal Year End Date Current Fiscal Year End Date Investment Type Investment Type [Axis] Exercise price Share Based Compensation Arrangement Fair Value Assumptions Exercise Price Share based compensation arrangement fair value assumptions exercise price. Financial Instruments Transfers And Servicing Of Financial Instruments Types Of Financial Instruments [Domain] Research and development funding charges Research And Development Funding Charges Research and development funding charges. Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total Cash and cash equivalents at the beginning of the period Cash and cash equivalents at the end of the period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations Accrued research and development expenses Increase Decrease In Accrued Research And Development Expenses Increase (decrease) in accrued research and development expenses. Other assets Other Assets Noncurrent Entity Address, Address Line One Entity Address Address Line1 Number of additional undisclosed viral targets Number Of Additional Undisclosed Viral Targets Number of additional undisclosed viral targets. Accrued expenses: Accrued Liabilities Current [Abstract] 2020 At the Market Offerings Two Thousand And Twenty At The Market Offerings [Member] Two thousand and twenty at the market offerings. Subsidiary Sale Of Stock [Line Items] Subsidiary Sale Of Stock [Line Items] Capitalized and amortized costs period Capitalized And Amortized Costs Period Capitalized and amortized costs period. Vesting [Axis] Preferred stock, shares issued Preferred Stock Shares Issued Balance Sheet Location Balance Sheet Location [Domain] Other accrued expenses Other Accrued Liabilities Current Door Pharma Agreement Door Pharma Agreement [Member] Door pharma agreement. Payments to Acquire Property, Plant, and Equipment, Total Purchases of property and equipment Payments To Acquire Property Plant And Equipment Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs (share) Stock Issued During Period Shares New Issues Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures, Total Issuance of common stock for settlement of restricted stock units (RSUs) Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures Level 2 Fair Value By Fair Value Hierarchy Level [Axis] 2018 ESPP Two Thousand Eighteen Employee Stock Purchase Plan [Member] TwoThousandEighteenEmployeeStockPurchasePlanMember Schedule Of Research And Development Arrangement Contract To Perform For Others [Table] Schedule Of Research And Development Arrangement Contract To Perform For Others [Table] Incremental costs Incremental Costs Incremental costs. Equity [Abstract] Option, Forfeited Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price Loss from operations Operating Income Loss Additional paid-in capital Additional Paid In Capital Common Stock Stock-based compensation arrangement by share-based payment award, requisite service period Share Based Compensation Arrangement By Share Based Payment Award Award Requisite Service Period1 Accrued professional fees and other Accrued Professional Fees Current Entity Filer Category Entity Filer Category Deferred Compensation Liability [Abstract] Option Indexed to Issuer's Equity, Type Option Indexed To Issuers Equity Type [Domain] Total operating expenses Operating Expenses Entity Current Reporting Status Entity Current Reporting Status Options vested and exercisable Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 Fair Value, Short-term marketable securities Short-term marketable securities Marketable securities - short-term Sale of Common Stock Stockholders Equity Note Disclosure [Text Block] Total stockholders' equity Balance Balance Stockholders Equity Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income [Member] Short-term marketable securities Short Term Investments [Member] Schedule of Investments in Marketable Securities Schedule Of Available For Sale Securities Reconciliation Table [Text Block] Entity Tax Identification Number Entity Tax Identification Number Accrued restructuring charges Accrued balance as of September 30, 2022 Accrued balance as of June 30, 2022 Accrued Restructuring Charges Current Accrued restructuring charges current. Income Statement Location Income Statement Location [Axis] Forfeited Forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period Common stock, $0.001 par value; 150,000,000 and 100,000,000 shares authorized as of September 30, 2022 and December 31, 2021, respectively; 48,481,194 and 48,120,437 shares issued and outstanding as of September 30, 2022 and December 31, 2021, respectively Common Stock Value Retained Earnings (Accumulated Deficit), Total Accumulated deficit Retained Earnings Accumulated Deficit Equity Components Statement Equity Components [Axis] Accrued research and development expenses Accrued Research And Development Expenses Current Accrued research and development expenses current. Gross Unrealized Loss Cash Equivalents At Carrying Value And Available For Sale Debt Securities Gross Unrealized Loss Cash equivalents at carrying value and available for sale debt securities gross unrealized loss. Entity Emerging Growth Company Entity Emerging Growth Company Operating expenses Operating Expenses [Abstract] Percentage of reduction in workforce Percentage Of Reduction In Workforce Percentage of reduction in workforce. Percentage of corporate alternative minimum tax Percentage of corporate alternative minimum tax. Proceeds from maturities of marketable securities Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities Expected term (years) Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 Operating lease liabilities Increase Decrease In Operating Lease Liabilities Increase decrease in operating lease liabilities. Total Intrinsic Value Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract] Document Transition Report Document Transition Report Number of shares sold Sale Of Stock Number Of Shares Issued In Transaction Total assets measured at fair value Assets Fair Value Disclosure Granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value Other Risks and Uncertainties Other Risks And Uncertainties Policy [Text Block] Other risks and uncertainties. Total other income Nonoperating Income Expense Depreciation, Depletion and Amortization, Total Depreciation and amortization Depreciation Depletion And Amortization Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures, Total Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares) Stock Issued During Period Shares Restricted Stock Award Net Of Forfeitures Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Accumulated other comprehensive loss Accumulated Other Comprehensive Income Loss Net Of Tax Accounts Receivable, after Allowance for Credit Loss, Current, Total Accounts receivable from collaborations Accounts Receivable Net Current Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Milestone and Research Agreements: Research And Development Arrangement Contract To Perform For Others [Line Items] Research And Development Arrangement Contract To Perform For Others [Line Items] Amortized Cost, Long-term marketable securities Debt Securities, Available-for-Sale, Amortized Cost, Noncurrent Net loss Net loss Net loss Net Income Loss Operating lease liabilities - short-term Operating Lease Liability Current Severance payments Supplemental Unemployment Benefits Severance Benefits Additional Paid-in Capital Additional Paid In Capital [Member] Collaborative Arrangement and Arrangement Other than Collaborative Arrangements And Nonarrangement Transactions [Member] Cash equivalents Cash Equivalents At Fair Value [Abstract] Cash equivalents at fair value. Entity Registrant Name Entity Registrant Name Amortized Cost Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Summary of Assumptions Used to Estimate Fair Values of Stock Options Grants Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block] U.S and foreign corporate debt securities U S Government Agencies Debt Securities [Member] Share-Based Payment Arrangement, Noncash Expense, Total Stock-based compensation Share Based Compensation Other Accrued Expenses Other Accrued Expenses [Member] Other accrued expenses. Property, Plant and Equipment, Net, Total Property and equipment, net Property Plant And Equipment Net Award Type Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Statement [Line Items] Statement [Line Items] Retention bonuses costs Retention Bonuses Costs Retention bonuses costs. Title of 12(b) Security Security12b Title Increase (Decrease) in Accounts Payable, Total Accounts payable Increase Decrease In Accounts Payable Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Common Stock Common Stock [Member] Cash flows from operating activities Net Cash Provided By Used In Operating Activities [Abstract] Equity Component Equity Component [Domain] Purchases of marketable securities Payments To Acquire Available For Sale Securities Debt Entity Address, State or Province Entity Address State Or Province Schedule of Accrued Restructuring Charges Schedule Of Accrued Restructuring Charges [Table TextBlock] Schedule of accrued restructuring charges. Geographical Statement Geographical [Axis] Milestones And Research Agreements [Abstract] Milestones and Research Agreements Net increase in cash and cash equivalents Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Document Type Document Type Entity Shell Company Entity Shell Company Stock-based compensation expense Allocated Share Based Compensation Expense Fair value assets transfers between level 1, level 2 or level 3 Fair Value Assets Between Levels Transfers Amount Fair value assets between levels transfers amount. Gross Unrealized Gain, Long-term marketable securities Available For Sale Debt Securities Accumulated Gross Unrealized Gain before Tax Noncurrent Available for sale debt securities accumulated gross unrealized gain before tax noncurrent. Total fair value of awards Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Amount The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. Security Exchange Name Security Exchange Name Antidilutive Securities Excluded from Computation of Earnings Per Share Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Net cash used in operating activities Net Cash Provided By Used In Operating Activities Unrecognized stock-based compensation expense expected to be recognized, term Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 Options Outstanding, Weighted Average Remaining Contractual Term (Years) Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 Amortized Cost, Short-term marketable securities Debt Securities, Available-for-Sale, Amortized Cost, Current Unvested RSUs RSUs Restricted Stock Units R S U [Member] Amortized Cost Cash Equivalents At Carrying Value And Available For Sale Debt Securities Amortized Cost Cash equivalents at carrying value and available for sale debt securities amortized cost. Summary of Stock Option Activity and Related Information Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding, Beginning Balance Common stock, shares outstanding Common Stock Shares Outstanding Level 2 Fair Value Inputs Level2 [Member] Cash flows from investing activities Net Cash Provided By Used In Investing Activities [Abstract] Commitments and contingencies Commitments And Contingencies Common stock, shares issued Common Stock Shares Issued U.S. treasury securities U S Treasury Securities [Member] Minimum Minimum [Member] BeiGene Agreement Bei Gene Agreement [Member] BeiGene agreement. Options vested and exercisable Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Total accrued expenses Accrued Liabilities Current Share-Based Compensation Arrangement by Share-Based Payment Award, Option, Nonvested, Weighted Average Exercise Price, Ending Balance Share-Based Compensation Arrangement by Share-Based Payment Award, Option, Nonvested, Weighted Average Exercise Price, Beginning Balance Options grant date fair value Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Weighted Average Grant Date Fair Value Stockholders' equity Stockholders Equity [Abstract] Schedule Of Available For Sale Securities [Table] Schedule Of Available For Sale Securities [Table] Entity Address, Address Line Two Entity Address Address Line2 Cash and Cash Equivalents Cash And Cash Equivalents [Axis] Forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value Award Type Award Type [Axis] Subsequent Event Subsequent Event [Member] Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Significant accounting policies. Other income Nonoperating Income Expense [Abstract] Research and Development Expense, Total Research and development expense Research and development Research And Development Expense Restructuring Type Restructuring Cost And Reserve [Axis] Entity Central Index Key Entity Central Index Key Milestone payment, diligence maintenance fees Milestone Payment Diligence Maintenance Fees Milestone payment, diligence maintenance fees. Reductions for cash payments Payments for Restructuring Weighted Average Fair Value Per RSU at Grant Price Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Intrinsic Value Roll Forward Numerator: Net Income Loss [Abstract] Accounting Policies [Abstract] Investments Debt And Equity Securities [Abstract] Investments in marketable securities: Schedule Of Available For Sale Securities [Line Items] Expected volatility Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate U.S. and foreign commercial paper U S And Foreign Commercial Paper [Member] U.S. and foreign commercial paper. Measurement Frequency Fair Value By Measurement Frequency [Axis] Stock Plans and Stock-Based Compensation Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Subsequent Event [Table] Subsequent Event [Table] General and Administrative Expense, Total General and administrative General And Administrative Expense Organization Consolidation And Presentation Of Financial Statements [Abstract] Options, Outstanding at beginning of period Option, Outstanding at end of period Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Research and Development Research and Development Expenses Research And Development Expense [Member] Operating lease liabilities arising from obtaining ROU assets Right Of Use Asset Obtained In Exchange For Operating Lease Liability Adjustments to reconcile net loss to net cash used in operating activities: Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Accumulated Deficit Retained Earnings [Member] Money market fund Money Market Funds [Member] Compensation expense: Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Gain (Loss) on Disposition of Property Plant Equipment, Total Loss on disposal of property and equipment Gain Loss On Sale Of Property Plant Equipment Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others By Type [Axis] Arbutus Biopharma Agreement Arbutus Biopharma Agreement [Member] Arbutus biopharma agreement. Entity Interactive Data Current Entity Interactive Data Current Issuance of common stock upon cashless exercise of pre-funded warrants (in shares) Issuance Of Common Stock Upon Cashless Exercise Of Pre Funded Warrants Shares Issuance of common stock upon cashless exercise of pre-funded warrants shares. Supplemental non-cash investing and financing activities Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Restructuring and is expected amount, total Restructuring And Is Expected Amount Total Restructuring and is expected amount, total. Net proceeds from the issuance of common stock through equity plans Proceeds From Issuance Initial Public Offering Local Phone Number Local Phone Number Schedule of Earnings Per Share, Basic and Diluted Schedule Of Earnings Per Share Basic And Diluted Table [Text Block] Employees Including Executive Officers Employees Including Executive Officers [Member] Employees including executive officers. Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant accounting policies. Share-based Compensation Arrangement by Share-based Payment Award Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Basis of Presentation Basis Of Accounting Policy Policy [Text Block] Options vested and exercisable Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Option, Granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross Income Statement Location Income Statement Location [Domain] Outstanding awards Beginning of period Ending of period Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Balance (in shares) Balance (in shares) Shares Outstanding Prepaid expenses and other current assets Increase Decrease In Prepaid Deferred Expense And Other Assets Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Sixth Amended And Restated Certificate Of Incorporation Sixth Amended And Restated Certificate Of Incorporation [Member] Sixth amended and restated certificate of incorporation. Options Options, Outstanding at beginning of period Option, Outstanding at end of period Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Document Fiscal Year Focus Document Fiscal Year Focus Remeasurement of lease liabilities arising from modification of ROU assets Remeasurement Of Lease Liabilities Arising From Modification Of Right Of Use Assets Remeasurement of lease liabilities arising from modification of right of use assets. Schedule of Fair Value of Financial Assets Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Table [Text Block] Antios Agreement Antios Agreement [Member] Antios agreement. Vesting [Domain] Earnings Per Share, Basic, Total Net loss per share - basic Net loss per share, basic Earnings Per Share Basic Weighted Average Exercise Price Per Share Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Rollforward Proceeds from the issuance of common stock under ESPP Proceeds From Issuance Of Common Stocks Under Employee Stock Purchase Plan Proceeds from issuance of common stocks under employee stock purchase plan. ASSETS Assets [Abstract] Prepaid expenses and other current assets Prepaid Expense And Other Assets Current Financial Instrument Financial Instrument [Axis] Non-cash rent expense Noncash Rent Expense Represent non cash rent expense. Common stock subject to purchase under ESPP Common Stock Subject To Purchase Under Employee Stock Purchase Program [Member] Common stock subject to purchase under employee stock purchase program. Schedule of Restructuring and Related Costs [Table] Long-term marketable securities Long Term Marketable Securities [Member] Long term marketable securities. Number of Shares Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities And Stockholders Equity [Abstract] Potential milestone payment Purchase Commitment Remaining Minimum Amount Committed Antidilutive Securities, Name Antidilutive Securities Name [Domain] Type of Restructuring Type Of Restructuring [Domain] Summary of Restricted Stock Units and Related Information Nonvested Restricted Stock Shares Activity Table [Text Block] Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total Net loss Profit Loss Current assets Assets Current [Abstract] Long-term marketable securities Long Term Investments [Abstract] Long-term marketable securities Fair Value, Long-term marketable securities Available For Sale Securities Debt Securities Noncurrent Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Gross Unrealized Gain Cash And Cash Equivalent Gross Unrealized Gain Cash and cash equivalent gross unrealized gain. Payables And Accruals [Abstract] Measurement Frequency Fair Value Measurement Frequency [Domain] Net amortization of investments in marketable debt securities Amortization Of Investments In Marketable Debt Securities Amortization of investments In marketable debt securities. Changes in operating assets and liabilities: Increase Decrease In Operating Capital [Abstract] Collaboration Agreements Collaborative And License Arrangement Disclosure [Text Block] Collaborative and License Arrangement Disclosure. Restructuring Restructuring and Related Activities Disclosure [Text Block] Accrued restructuring charges Accrued Restructuring Charges Accrued restructuring charges. Cover [Abstract] License agreement term License Agreement Term License agreement term. Vested Performance-based vesting conditions Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Current liabilities Liabilities Current [Abstract] Maximum Maximum [Member] Unrealized loss on marketable debt securities Unrealized loss on marketable securities Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Schedule of Recognized Stock-Based Compensation Expense Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Initial public offering value of shares authorized Initial Public Offering Value Of Shares Authorized The value of common stock authorized to issue in a public offering. Net cash provided by investing activities Net Cash Provided By Used In Investing Activities Issuance of common stock upon cashless exercise of pre-funded warrants Issuance Of Common Stock Upon Cashless Exercise Of Pre Funded Warrants Issuance of common stock upon cashless exercise of pre-funded warrants. Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Options exercised Stock Issued During Period Shares Stock Options Exercised Gross Unrealized Loss, Short-term marketable securities Available for Sale Debt Securities Accumulated Gross Unrealized Loss before Tax Current Available for sale debt securities accumulated gross unrealized loss before tax current. Level 3 Fair Value Inputs Level3 [Member] Use of Estimates Use Of Estimates Common stock, shares authorized Common Stock Shares Authorized Trading Symbol Trading Symbol Title of Individual Title Of Individual With Relationship To Entity [Domain] Subsequent Event Type Subsequent Event Type [Axis] Balance Sheet Location Balance Sheet Location [Axis] Comprehensive loss Comprehensive Income Net Of Tax Risk-free rate Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Proceeds from Sale of Property, Plant, and Equipment, Total Proceeds from sale of property and equipment Proceeds From Sale Of Property Plant And Equipment Accounts Payable, Current, Total Accounts payable Accounts Payable Current Plan Name Plan Name [Axis] Title of Individual Title Of Individual [Axis] Restructuring costs incurred Restructuring charges Restructuring And Related Cost Incurred Cost Benefit Restructuring and related cost incurred cost benefit Common stock, par value Common Stock Par Or Stated Value Per Share Retained Employees Retained Employees [Member] Retained employees. Granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Option, Granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Antidilutive securities excluded from computation of loss per share Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Fair Value Cash equivalents Cash And Cash Equivalents Fair Value Disclosure Employee Severance And Related Benefits Employee Severance And Related Benefits [Member] Employee severance and related benefits. Other assets Increase Decrease In Other Noncurrent Assets