Entity Central Index Key Cover [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity File Number Entity File Number Entity Tax Identification Number Entity Tax Identification Number Entity Current Reporting Status Entity Current Reporting Status Entity Shell Company Entity Shell Company Entity Address, Address Line One Entity Address Address Line1 Entity Address, City or Town Entity Address City Or Town Entity Address, State or Province Entity Address State Or Province Entity Address, Postal Zip Code Entity Address Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Entity Interactive Data Current Entity Interactive Data Current Title of 12(b) Security Security12b Title Security Exchange Name Security Exchange Name Entity Incorporation, State or Country Code Entity Incorporation State Country Code Document Quarterly Report Document Quarterly Report Document Transition Report Document Transition Report Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Early Exercised Stock Options Liability. Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Short-term marketable securities Short Term Investments Related party receivable from collaboration Contract With Customer Asset Net Current Prepaid expenses and other current assets Prepaid Expense And Other Assets Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net Restricted cash Restricted Cash Noncurrent Other non-current assets Other Assets Noncurrent Total assets Assets Liabilities and stockholders' equity Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable Accounts Payable Current Accrued liabilities Accrued Liabilities Current Deferred rent, current Deferred Rent Credit Current Deferred revenue, current Contract With Customer Liability Current Total current liabilities Liabilities Current Deferred rent, non-current Deferred Rent Credit Noncurrent Other non-current liabilities Other Liabilities Noncurrent Early exercise stock option liability Early Exercised Stock Options Liability Total liabilities Liabilities Commitments and contingencies (Note 6) Commitments And Contingencies Stockholders' equity: Stockholders Equity [Abstract] Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding as of March 31, 2020 and December 31, 2019, respectively Preferred Stock Value Common stock, $0.001 par value; 400,000,000 shares authorized; 67,936,438 and 66,960,279 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated other comprehensive gain (loss) Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated deficit Retained Earnings Accumulated Deficit Total stockholders' equity Stockholders Equity Total liabilities and stockholders' equity Liabilities And Stockholders Equity Preferred stock, par value Preferred Stock Par Or Stated Value Per Share Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares issued Preferred Stock Shares Issued Preferred stock, shares outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Income Statement [Abstract] Related party revenue Revenue From Contract With Customer Excluding Assessed Tax Operating expenses: Operating Expenses [Abstract] Research and development Research And Development Expense General and administrative General And Administrative Expense Total operating expenses Operating Expenses Loss from operations Operating Income Loss Interest income Interest Income Expense Nonoperating Net Other income (expense), net Other Nonoperating Income Expense Net loss Net Income Loss Net loss per share, basic and diluted Earnings Per Share Basic And Diluted Weighted average shares used to compute net loss per share, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Statement Of Income And Comprehensive Income [Abstract] Net Loss Other comprehensive gain (loss), net of tax: Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent [Abstract] Net unrealized gain (loss) on available-for-sale marketable securities Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Total comprehensive loss Comprehensive Income Net Of Tax Stock issued during period shares vesting of early exercised stock options. Stock issued during period value vesting of early exercised stock options. Statement Of Stockholders Equity [Abstract] Statement [Table] Statement [Table] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock Common Stock [Member] Additional Paid-In Capital Additional Paid In Capital [Member] Other Comprehensive Gain (Loss) Accumulated Other Comprehensive Income [Member] Accumulated Deficit Retained Earnings [Member] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Convertible Preferred Stock Convertible Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Balance Balance, shares Shares Outstanding Issuance of common stock under 401(k) Plan Stock Issued During Period Value Employee Benefit Plan Issuance of common stock under 401(k) Plan, shares Stock Issued During Period Shares Employee Benefit Plan Issuance of common stock upon exercise of stock options Stock Issued During Period Value Stock Options Exercised Issuance of common stock upon exercise of stock options, shares Stock Issued During Period Shares Stock Options Exercised Vesting of common stock from early exercises Stock Issued During Period Value Vesting Of Early Exercised Stock Options Vesting of common stock from early exercises, shares Stock Issued During Period Shares Vesting Of Early Exercised Stock Options Stock-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Changes in unrealized (loss) gain on available-for-sale securities Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Net exercise of preferred stock warrant to Series A preferred stock Stock And Warrants Issued During Period Value Preferred Stock And Warrants Stock and warrants issued during period shares preferred stock and warrants. Net exercise of preferred stock warrant to Series A preferred stock, shares Stock And Warrants Issued During Period Shares Preferred Stock And Warrants Cumulative effect adjustment upon adoption of ASU 2014-09 New Accounting Pronouncement Or Change In Accounting Principle Effect Of Adoption Quantification Net loss Balance Balance, shares Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] IPO I P O [Member] Private Placement Private Placement [Member] Number of shares issued in transaction Stock Issued During Period Shares New Issues Proceeds from issuance of common stock upon initial public offering, net Proceeds From Issuance Initial Public Offering Reclassification to common stock and additional paid-in capital Reclassifications Of Temporary To Permanent Equity Proceeds from issuance of common stock upon completion of private placement Proceeds From Issuance Of Private Placement Net exercise of convertible preferred stock warrant to Series A preferred stock. Vesting of common stock from early exercises. Cost of property and equipment purchases accrued but not yet paid. Deferred IPO costs accrued but not yet paid. Statement Of Cash Flows [Abstract] Cash flows from operating activities Net Cash Provided By Used In Operating Activities [Abstract] Net loss Profit Loss 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] Depreciation Depreciation Amortization of discount on marketable securities Accretion Amortization Of Discounts And Premiums Investments Stock-based compensation expense Share Based Compensation Other non-cash expenses Other Noncash Income Expense Changes in operating assets and liabilities: Increase Decrease In Operating Capital [Abstract] Related party receivable from collaboration Increase Decrease In Accounts Receivable Related Parties Prepaid expenses and other assets Increase Decrease In Prepaid Deferred Expense And Other Assets Accounts payable Increase Decrease In Accounts Payable Accrued expenses and other liabilities Increase Decrease In Accrued Liabilities And Other Operating Liabilities Deferred rent Increase Decrease In Prepaid Rent Deferred revenue Increase Decrease In Contract With Customer Liability Net cash used in operating activities Net Cash Provided By Used In Operating Activities Cash flows from investing activities Net Cash Provided By Used In Investing Activities [Abstract] Purchase of marketable securities Payments To Acquire Marketable Securities Proceeds from sales and maturities of marketable securities Proceeds From Sale And Maturity Of Marketable Securities Purchase of property and equipment Payments To Acquire Machinery And Equipment Net cash provided by investing activities Net Cash Provided By Used In Investing Activities Cash flows from financing activities Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from issuance of common stock upon exercise of stock options Proceeds From Stock Options Exercised Payments of deferred financing costs Payments Of Stock Issuance Costs Net cash provided by (used in) financing activities Net Cash Provided By Used In Financing Activities Net increase (decrease) in cash and cash equivalents Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Cash, cash equivalents and restricted cash at beginning of period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Cash, cash equivalents and restricted cash at end of period Non-cash investing and financing activities: Noncash Investing And Financing Items [Abstract] Net exercise of convertible preferred stock warrant to Series A preferred stock Net Exercise Of Convertible Preferred Stock Warrant To Series A Preferred Stock Vesting of common stock from early exercises Vesting Of Common Stock From Early Exercises Cost of property and equipment purchases accrued but not yet paid Cost Of Property And Equipment Purchases Accrued But Not Yet Paid Deferred IPO costs accrued but not yet paid Deferred I P O Costs Accrued But Not Yet Paid Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization and Description of Business Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Balance Sheet Components Supplemental Balance Sheet Disclosures [Text Block] Collaboration and license agreement disclosure. Collaboration And License Agreement Disclosure [Abstract] Research Collaboration and License Agreements Collaborative Arrangement Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Equity [Abstract] Stockholders' Equity Stockholders Equity Note Disclosure [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Basis of presentation and principles of consolidation. Basis of Presentation and Principles of Consolidation Basis Of Presentation And Principles Of Consolidation Policy [Text Block] Use of Estimates Use Of Estimates Need for additional capital. Need for Additional Capital Need For Additional Capital Policy [Text Block] Fair Value of Financial Instruments Fair Value Of Financial Instruments Policy Cash and Cash Equivalents Cash And Cash Equivalents Unrestricted Cash And Cash Equivalents Policy Marketable Securities Marketable Securities Policy Restricted Cash Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Concentration of Credit and Other Risks Concentration Risk Credit Risk Property and Equipment, Net Property Plant And Equipment Policy [Text Block] Leases Lessee Leases Policy [Text Block] Impairment of Long-Lived Assets Impairment Or Disposal Of Long Lived Assets Policy [Text Block] Income Taxes Income Tax Policy [Text Block] Revenue Recognition Revenue From Contract With Customer Policy [Text Block] Research and Development Research And Development Expense Policy Stock-Based Compensation Share Based Compensation Option And Incentive Plans Policy Foreign Currency Transactions Foreign Currency Transactions And Translations Policy [Text Block] Comprehensive Loss Comprehensive Income Policy Policy [Text Block] Net Loss per Share Earnings Per Share Policy [Text Block] Segment and Geographical Information Segment Reporting Policy Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Schedule of estimated useful life of asset. Estimated Useful Life of Asset Schedule Of Estimated Useful Life Of Asset Table [Text Block] Computation of Net Loss Per Common Share Schedule Of Earnings Per Share Basic And Diluted Table [Text Block] Potentially Dilutive Securities Not Included in Diluted Per Share Calculations Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Summary of Cash and Cash Equivalents and Marketable Securities Classified as Available-for-sale Securities Schedule Of Available For Sale Securities Reconciliation Table [Text Block] Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Schedule of Reconciliation of Cash, Cash Equivalent and Restricted Cash Schedule Of Restricted Cash And Cash Equivalents [Text Block] Property and Equipment Property Plant And Equipment [Text Block] Accrued Liabilities Schedule Of Accrued Liabilities Table [Text Block] Schedule of Milestone Payments by Indications Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions Table [Text Block] Schedule of recognized revenue from collaboration and license arrangements. Schedule of Recognized Revenue from Collaboration and License Agreements Schedule Of Recognized Revenue From Collaboration And License Arrangements Table [Text Block] Schedule of Changes in Related Party Contract Liabilities Contract With Customer Asset And Liability Table [Text Block] Future Minimum Commitments under Unassigned Lease Obligations Schedule Of Future Minimum Rental Payments For Operating Leases Table [Text Block] Schedule of Shares of Common Stock Reserved for Issuance Schedule Of Stock By Class [Text Block] Summary of Activity under 2008 Plan and 2018 Plan Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Summary of Stock Based Compensation Expense Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Place of incorporation Date of incorporation Entity Incorporation Date Of Incorporation Summary of significant accounting policies. Summary of significant accounting policies Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Concentration Risk Benchmark Concentration Risk By Benchmark [Axis] Concentration Risk Benchmark Concentration Risk Benchmark [Domain] Revenue Sales Revenue Net [Member] Concentration Risk Type Concentration Risk By Type [Axis] Concentration Risk Type Concentration Risk Type [Domain] Customer Concentration Risk Customer Concentration Risk [Member] Customer Major Customers [Axis] Customer Name Of Major Customer [Domain] Merck. Merck Merck [Member] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Net losses Accumulated deficit Cash, cash equivalents and marketable securities Cash Cash Equivalents And Short Term Investments Impairment related to other-than-temporary Other Than Temporary Impairment Loss Debt Securities Available For Sale Percentage of revenue Concentration Risk Percentage1 Property Plant And Equipment [Abstract] Schedule Of Property Plant And Equipment [Table] Schedule Of Property Plant And Equipment [Table] Property, Plant and Equipment, Type Property Plant And Equipment By Type [Axis] Property, Plant and Equipment, Type Property Plant And Equipment Type [Domain] Computer Equipment Computer Equipment [Member] Laboratory equipment and office furniture. Laboratory Equipment and Office Furniture Laboratory Equipment And Office Furniture [Member] Leasehold Improvement Leasehold Improvements [Member] Property Plant And Equipment [Line Items] Property Plant And Equipment [Line Items] Estimated useful life of asset Property Plant And Equipment Useful Life Leasehold improvement Property Plant And Equipment Estimated Useful Lives Net unrealized gain (loss) on marketable securities Marketable Securities Unrealized Gain Loss Earnings Per Share [Abstract] Numerator: Net Income Loss [Abstract] Denominator: Earnings Per Share Basic And Diluted Other Disclosures [Abstract] Net loss per share—basic and diluted 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] Subsidiary Sale Of Stock [Line Items] Subsidiary Sale Of Stock [Line Items] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Shares Committed Under ESPP Employee Stock [Member] Convertible Preferred Stock Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Antidilutive Securities, Name Antidilutive Securities Name [Domain] Options to purchase common stock. Options to Purchase Common Stock Options To Purchase Common Stock [Member] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Potentially dilutive securities not included in calculations of diluted per share Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Number of operating business segment Number Of Operating Segments Schedule Of Available For Sale Securities [Table] Schedule Of Available For Sale Securities [Table] Investment Type Investment Type [Axis] Investments Investment Type Categorization [Member] Money Market Funds Money Market Funds [Member] Corporate and Agency Bonds Corporate Bond Securities [Member] Commercial Paper Commercial Paper [Member] U.S. Government Agencies Securities U S Government Agencies Debt Securities [Member] Cash and Cash Equivalents Cash And Cash Equivalents [Member] Short-term Marketable Securities Short Term Investments [Member] Schedule Of Available For Sale Securities [Line Items] Schedule Of Available For Sale Securities [Line Items] Amortized Cost Available For Sale Debt Securities Amortized Cost Basis Gross Unrealized Gain Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax Gross Unrealized Loss Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax Fair Value Available For Sale Securities Debt Securities Amortized Cost Cash on deposit with banks Interest Bearing Deposits In Banks Number of marketable securities in unrealized loss positions less than 12 months Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Number Of Positions Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Measurement Frequency Fair Value By Measurement Frequency [Axis] Measurement Frequency Fair Value Measurement Frequency [Domain] Fair Value Measurements, Recurring Fair Value Measurements Recurring [Member] Asset Class Fair Value By Asset Class [Axis] Asset Class Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation By Asset Class [Domain] Corporate and Agency Bonds Corporate Debt Securities [Member] Level 2 Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Level 1 Fair Value Inputs Level1 [Member] Level 2 Fair Value Inputs Level2 [Member] Level 3 Fair Value Inputs Level3 [Member] 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] Assets: Assets Fair Value Disclosure [Abstract] Assets fair value Assets Fair Value Disclosure Fair value, assets, level 1 to level 2 transfers, amount Fair Value Assets Level1 To Level2 Transfers Amount Fair value, assets, level 2 to level 1 transfers, amount Fair Value Assets Level2 To Level1 Transfers Amount Fair value, liabilities, level 1 to level 2 transfers, amount Fair Value Liabilities Level1 To Level2 Transfers Amount Fair value, liabilities, level 2 to level 1 transfers, amount Fair Value Liabilities Level2 To Level1 Transfers Amount Total cash, cash equivalents and restricted cash Construction In Process Construction In Progress [Member] Property and equipment, gross Property Plant And Equipment Gross Less: accumulated depreciation and amortization Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Total property and equipment, net Depreciation expense Accrued expenses current. Accrued clinical trials and research and development costs current. Accrued personnel expense current. Accrued Manufacturing costs current. Accrued expenses Accrued Expenses Current Clinical trials and research and development costs Accrued Clinical Trials And Research And Development Costs Current Personnel-related costs Accrued Personnel Expense Current Manufacturing costs Accrued Manufacturing Costs Current Total accrued liabilities Collaborative arrangement up front payment received. Fair value of assets and services exchanged allocated to equity component. Fair value of assets and services exchanged allocated to revenue component. Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Collaborative Arrangement and Arrangement Other than Collaborative Type Of Arrangement [Axis] Collaborative Arrangement and Arrangement Other than Collaborative Arrangements And Nonarrangement Transactions [Member] Collaboration Agreement Collaborative Arrangement [Member] Related Party Related Party Transactions By Related Party [Axis] Related Party Related Party [Domain] Merck Sharp and Dohme Corporation. Merck Sharp & Dohme Corp Merck Sharp And Dohme Corporation [Member] Series E convertible preferred stock. Series E Convertible Preferred Stock Series E Convertible Preferred Stock [Member] Statistical Measurement Range [Axis] Statistical Measurement Range [Member] Maximum Maximum [Member] Minimum Minimum [Member] Small molecule compounds. Small Molecule Compounds Small Molecule Compounds [Member] Side letter agreement. Side Letter Agreement Side Letter Agreement [Member] Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Upfront payment received Collaborative Arrangement Up Front Payment Received Preferred stock, shares issued Temporary Equity Shares Issued Preferred stock, price per share Temporary Equity Par Or Stated Value Per Share Proceeds from issuance of preferred stock Proceeds From Issuance Of Convertible Preferred Stock Fair values of assets and services exchanged allocated to equity component Fair Value Of Assets And Services Exchanged Allocated To Equity Component Fair values of assets and services exchanged allocated to revenue component Fair Value Of Assets And Services Exchanged Allocated To Revenue Component Term of agreement. Collaborative arrangement annual funding amount over agreement term. Research and development performance additional option extend term. Term of agreement Term Of Agreement Collaborative arrangement funding, amount Collaborative Arrangement Annual Funding Amount Over Agreement Term Research and development services additional option extend term Research And Development Performance Additional Option Extend Term Development and regulatory milestone payments received. Commercial milestone payments received License fee receivable. License fee License Fee Receivable Development and regulatory milestone payments received Development And Regulatory Milestone Payments Received Commercial milestone payments received Commercial Milestone Payments Received Initial research term. Research collaboration and license agreements extension fee. Research and development option extend term. Initial research term Initial Research Term Research collaboration and license agreements extension fee Research Collaboration And License Agreements Extension Fee Additional term Research And Development Option Extend Term Research and development collaboration agreement additional term description. Amount of fund received for research activities. Amount of additional fund received for research activities Research and Development Collaboration Agreement Additional Term Description Research And Development Collaboration Agreement Additional Term Description Amount of fund received for research activities Amount Of Fund Received For Research Activities Amount of additional fund received for research activities Amount Of Additional Fund Received For Research Activities Research and development service performance period. Number of options to extend performance of research program. Performance of R&D services period Research And Development Service Performance Period Number of options to extend performance of research program Number Of Options To Extend Performance Of Research Program Upfront fee. Collaborative Agreement Consideration Milestone. Upfront Fee Upfront Fee Collaborative agreement milestone or other forms of consideration Collaborative Agreement Consideration Milestone Received amount from options. Received amount from options Received Amount From Options Deferred revenue Contract With Customer Liability Deferred revenue recognized Contract With Customer Liability Revenue Recognized Collaboration and license revenue Percentage of common stock shares outstanding owned by related party. Common stock purchased by related party Sale Of Stock Number Of Shares Issued In Transaction Public offering price of common stock Sale Of Stock Price Per Share Percentage of outstanding shares of common stock owned by related party Percentage Of Common Stock Shares Outstanding Owned By Related Party Eligible to receive one-time payment for licensed program. Eligible milestone payments receivable. Eligible milestone payment receivable upon potential achievement of specific clinical development events. Eligible milestone payment receivable upon potential achievement of certain regulatory events. One-time payment Eligible To Receive One Time Payment For Licensed Program Milestone payments Eligible Milestone Payments Receivable Milestone payments relates to potential achievement of specific clinical development events Eligible Milestone Payment Receivable Upon Potential Achievement Of Specific Clinical Development Events Milestone payments relates to potential achievement of certain regulatory events Eligible Milestone Payment Receivable Upon Potential Achievement Of Certain Regulatory Events Milestone payment for potential achievement of certain clinical development events. Research collaboration and license agreements. Research Collaboration And License Agreements [Abstract] Project Capitalized Costs Of Unproved Properties Excluded From Amortization By Property Or Project [Axis] Project Project [Member] First indication. First Indication First Indication [Member] Second indication. Second Indication Second Indication [Member] Third indication. Third Indication Third Indication [Member] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others By Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others Type [Domain] Clinical trial to first patient in first phase three. Clinical Trial to First Patient in First Phase 3 Clinical Trial To First Patient In First Phase Three [Member] Capitalized Contract Cost Capitalized Contract Cost [Axis] Capitalized Contract Cost Capitalized Contract Cost [Domain] Geographical Statement Geographical [Axis] Geographical Segment Geographical [Domain] United States UNITED STATES European Union European Union [Member] Japan JAPAN Upon administration of an applicable product to the first patient in the first Phase 3 clinical trial for such product for the given indication Milestone Payment For Potential Achievement Of Certain Clinical Development Events Milestone payment for potential achievement of certain regulatory events. Milestone payments in connection with potential achievement of certain regulatory events Milestone Payment For Potential Achievement Of Certain Regulatory Events Disclosure Research Collaboration And License Agreements Schedule Of Recognized Revenue From Collaboration And License Agreements Details [Abstract] Disclosure Research Collaboration And License Agreements Schedule Of Recognized Revenue From Collaboration And License Agreements Details [Abstract] Related party revenue Revenue From Related Parties Eligible to receive commercial milestone payments for each licensed product. Upfront license fee. Upfront license fee Upfront License Fee Eligible to receive commercial milestone payments Eligible To Receive Commercial Milestone Payments For Each Licensed Product Beginning Balance Revenue recognized through March 16, 2020 Ending Balance Contract assets Contract With Customer Asset Net Operating lease agreement amendment period. Operating lease expiration period. Commitments and contingencies disclosure. Commitments and contingencies disclosure. Commitments And Contingencies Disclosure [Table] Commitments And Contingencies Disclosure [Table] Lease Arrangement, Type Lease Arrangement Type [Axis] Lease Arrangement, Type Lease Arrangement Type [Domain] Corporate office space and laboratory facility. Corporate Office Space and Laboratory Facility Corporate Office Space And Laboratory Facility [Member] Credit Facility Credit Facility [Axis] Credit Facility Credit Facility [Domain] Letter of Credit Letter Of Credit [Member] Balance Sheet Location Balance Sheet Location [Axis] Balance Sheet Location Balance Sheet Location [Domain] Commitments And Contingencies Disclosure [Line Items] Commitments And Contingencies Disclosure [Line Items] Area of leased property Area Of Real Estate Property Operating lease agreement, amended period Operating Lease Agreement Amendment Period Operating lease agreement, expiration period Operating Lease Expiration Period Tenant improvement allowances Tenant Improvements Operating lease option additional extend term Lessee Operating Lease Renewal Term Total Leasehold improvements Operating lease term Lessee Operating Lease Term Of Contract Reduction in security deposit. Letter of credit as a security deposit Security Deposit Reduction in letter of credit on each 3rd anniversary and 4th anniversary Increase Decrease In Security Deposits Reduction in letter of credit Reduction In Security Deposit Remaining operating lease, payments from related party to lessor. Remaining lease payment obligation Remaining Operating Lease Payments From Related Party To Lessor Rent expense Operating Leases Rent Expense Net 2020 Operating Leases Future Minimum Payments Remainder Of Fiscal Year 2021 Operating Leases Future Minimum Payments Due In Two Years 2022 Operating Leases Future Minimum Payments Due In Three Years 2023 Operating Leases Future Minimum Payments Due In Four Years Total Operating Leases Future Minimum Payments Due Schedule Of Stock By Class [Table] Schedule Of Stock By Class [Table] Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] Stock option fiscal twenty eighteen plan. 2018 Plan Stock Option Fiscal Twenty Eighteen Plan [Member] Title of Individual Title Of Individual [Axis] Title of Individual Title Of Individual With Relationship To Entity [Domain] Non - employees. Non-employees Non Employees [Member] Class Of Stock [Line Items] Class Of Stock [Line Items] Stock repurchase plan, authorized shares Stock Repurchase Program Number Of Shares Authorized To Be Repurchased Common stock options outstanding. Common Stock Options Outstanding Common Stock Options Outstanding [Member] Common stock options available for grant. Common Stock Options Available for Grant Common Stock Options Available For Grant [Member] Four zero one k matching plan. 401(k) Matching Plan Four Zero One K Matching Plan [Member] Total Common Stock Capital Shares Reserved For Future Issuance Stock options, vesting period Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 Share based compensation arrangement by share based payment award options available for grants in period. Share based compensation arrangement by share based payment award options available for grant exercised in period. Share based compensation arrangement by share based payment award options available for grant forfeitures in period. Two thousand eight and two thousand eighteen plan. 2008 Plan and 2018 Plan Two Thousand Eight And Two Thousand Eighteen Plan [Member] Outstanding Options, Options Available for Grant, Beginning balance Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant Outstanding Options, Options Available for Grant, Additional Shares Share Based Compensation Arrangement By Share Based Payment Award Number Of Additional Shares Authorized Outstanding Options, Options Available for Grant, Granted Share Based Compensation Arrangement By Share Based Payment Award Options Available For Grants In Period Outstanding Options, Options Available for Grant, Exercised Share Based Compensation Arrangement By Share Based Payment Award Options Available For Grant Exercised In Period Outstanding Options, Options Available for Grant, Cancelled Share Based Compensation Arrangement By Share Based Payment Award Options Available For Grant Forfeitures In Period Outstanding Options, Options Available for Grant, Ending balance Outstanding Options, Number of Options, Beginning balance Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Outstanding Options, Number of Options, Granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross Outstanding Options, Number of Options, Exercised Outstanding Options, Number of Options, Cancelled Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period Outstanding Options, Number of Options, Ending balance Outstanding Options, Number of Options, Options vested and expected to vest Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number Outstanding Options, Number of Options, Options exercisable Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Outstanding Options, Weighted-Average Exercise Price, Beginning balance Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Outstanding Options, Weighted-Average Exercise Price, Granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Outstanding Options, Weighted-Average Exercise Price, Exercised Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price Outstanding Options, Weighted-Average Exercise Price, Cancelled Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price Outstanding Options, Weighted-Average Exercise Price, Ending balance Outstanding Options, Weighted-Average Exercise Price, Options vested and expected to vest Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Exercise Price Outstanding Options, Weighted-Average Exercise Price, Options exercisable Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Weighted Average Remaining Contractual Life (in Years) Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 Weighted Average Remaining Contractual Life (in Years), Vested and expected to vest Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term1 Weighted Average Remaining Contractual Life (in Years),Outstanding and Exercisable Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 Outstanding Options, Aggregate Intrinsic Value, Balance Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value Outstanding Options, Aggregate Intrinsic Value, Options vested and expected to vest-March 31, 2019 Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Aggregate Intrinsic Value Options Outstanding, Aggregate Intrinsic Value, Options exercisable-March 31, 2019 Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 Weighted-average grant date fair value of stock options ,Granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Intrinsic value of stock options exercised Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value Tax benefits realized Employee Service Share Based Compensation Tax Benefit From Compensation Expense 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] Employees and directors. Employees and Directors Employees And Directors [Member] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Research and Development Research And Development Expense [Member] General and Administrative General And Administrative Expense [Member] Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Stock-based compensation expense Allocated Share Based Compensation Expense Options granted CARES act of 2020 aid net operating loss carry forward period. Cares act of 2020 aid net operating losses carryforward maximum percentage of taxable income. CARES Act of 2020 aid net operating loss carry forward period C A R E S Act Of2020 Aid Net Operating Loss Carry Forward Period CARES Act of 2020 aid net operating losses carryforward maximum percentage of taxable income C A R E S Act Of2020 Aid Net Operating Losses Carryforward Maximum Percentage Of Taxable Income