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 Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Shell Company Entity Shell Company Title of 12(b) Security Security12b Title Security Exchange Name Security Exchange Name Entity File Number Entity File Number Entity Incorporation, State or Country Code Entity Incorporation State Country Code Entity Tax Identification Number Entity Tax Identification Number 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 Document Quarterly Report Document Quarterly Report Document Transition Report Document Transition Report Accrued research and development liability current. 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 Marketable Securities 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 Operating lease right-of-use asset Operating Lease Right Of Use Asset Restricted cash Restricted Cash Noncurrent Long-term marketable securities Marketable Securities Noncurrent Other long-term 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 Deferred rent, current portion Deferred Rent Credit Current Operating lease liability, current portion Operating Lease Liability Current Accrued research and development liabilities Accrued Research And Development Liability Current Accrued other liabilities Other Accrued Liabilities Current Accrued compensation Accrued Employee Benefits Current Total current liabilities Liabilities Current Long-term deferred rent Deferred Rent Credit Noncurrent Long-term operating lease liability Operating Lease Liability Noncurrent Commitments and contingencies (Note 7) Commitments And Contingencies Stockholders' equity Stockholders Equity [Abstract] Common stock, $0.0001 par value, 500,000,000 shares authorized at March 31, 2020 and December 31, 2019; 33,026,825 and 32,950,836 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated other comprehensive income 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 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] 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 Other income, net Other Nonoperating Income Expense Interest income Investment Income Interest Net loss Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest Net loss per share, basic and diluted Earnings Per Share Basic And Diluted Weighted-average shares used to calculate 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 income: Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent [Abstract] Net unrealized gain on available-for-sale securities Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Comprehensive loss Comprehensive Income Net Of Tax Stock issued during period shares stock options exercised and vested. Temporary equity value issuance of preferred stock from series C offering. Stock issued during period value common stock upon exercise of warrants. Statement Of Stockholders Equity [Abstract] Statement [Table] Statement [Table] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Common Stock Common Stock [Member] Additional Paid-In Capital Additional Paid In Capital [Member] Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income [Member] Accumulated Deficit Retained Earnings [Member] Adjustments for New Accounting Pronouncements Adjustments For New Accounting Pronouncements [Axis] Type of Adoption Type Of Adoption [Member] ASC 606 Accounting Standards Update201409 [Member] Statement [Line Items] Statement [Line Items] Balance Balance, Shares Stock-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Issuance of preferred stock from Series C offering Temporary Equity Value Issuance Of Preferred Stock From Series C Offering Conversion of preferred stock at initial public offering Stock Issued During Period Value Conversion Of Convertible Securities Conversion of preferred stock at initial public offering, Shares Stock Issued During Period Shares Conversion Of Convertible Securities Conversion of warrants at initial public offering Adjustments To Additional Paid In Capital Warrant Issued Exercise of stock options and vesting of early exercise shares Stock Issued During Period Value Stock Options Exercised Exercise of stock options and vesting of early exercise shares, Shares Stock Issued During Period Shares Stock Options Exercised And Vested Issuance of common stock from initial public offering Stock Issued During Period Value New Issues Issuance of stock from initial public offering, Shares Stock Issued During Period Shares New Issues Issuance of common stock upon exercise of warrants Stock Issued During Period Value Common Stock Upon Exercise Of Warrants Stock issued during period shares common stock upon exercise of warrants. Issuance of common stock upon exercise of warrants, Shares Stock Issued During Period Shares Common Stock Upon Exercise Of Warrants Issuance of shares under the Employee Stock Purchase Plan Stock Issued During Period Value Employee Stock Purchase Plan Issuance of shares under the Employee Stock Purchase Plan, Shares Stock Issued During Period Shares Employee Stock Purchase Plans Unrealized gain on available-for-sale securities Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent Cumulative-effect adjustment from adoption of ASC 606 accounting standard on revenue recognition Cumulative Effect On Retained Earnings Net Of Tax1 Balance Balance, Shares Increase (decrease) in deferred rent. Non-cash lease expense. Increase (decrease) in lease liability. Statement Of Cash Flows [Abstract] Operating activities: Net Cash Provided By Used In Operating Activities [Abstract] 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] Amortization of discount on marketable securities Accretion Amortization Of Discounts And Premiums Investments Depreciation Depreciation Stock-based compensation Share Based Compensation Deferred rent Increase Decrease In Deferred Rent Non-cash lease expense Non Cash Lease Expense Changes in operating assets and liabilities: Increase Decrease In Operating Capital [Abstract] Prepaid expenses and other assets Increase Decrease In Prepaid Deferred Expense And Other Assets Deferred revenue Increase Decrease In Contract With Customer Liability Accounts payable Increase Decrease In Accounts Payable Accrued liabilities Increase Decrease In Accrued Liabilities Lease liability Increase Decrease In Lease Liability Net cash used in operating activities Net Cash Provided By Used In Operating Activities Investing activities: Net Cash Provided By Used In Investing Activities [Abstract] Purchases of property and equipment Payments To Acquire Property Plant And Equipment Maturities of marketable securities Proceeds From Sale And Maturity Of Marketable Securities Purchases of marketable securities Payments To Acquire Marketable Securities Net cash provided by (used in) investing activities Net Cash Provided By Used In Investing Activities Financing activities: Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from issuances of common stock upon exercise of options and participation in employee stock purchase plan Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Net increase (decrease) in cash, cash equivalents and restricted cash 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 Supplemental disclosures of cash flow information Supplemental Cash Flow Information [Abstract] Non cash tenant improvement allowance used for leasehold improvements Payments For Proceeds From Tenant Allowance Purchases of property and equipment accrued but not yet paid Capital Expenditures Incurred But Not Yet Paid Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Investments Debt And Equity Securities [Abstract] Cash Equivalents and Marketable Securities Cash Cash Equivalents And Marketable Securities [Text Block] Balance Sheet Related Disclosures [Abstract] Balance Sheet Components Supplemental Balance Sheet Disclosures [Text Block] Research And Development [Abstract] License and Collaboration Agreements Collaborative Arrangement Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Stock-Based Compensation Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Earnings Per Share [Abstract] Net Loss per Share Earnings Per Share [Text Block] Basis of Presentation Basis Of Accounting Policy Policy [Text Block] Use of Estimates Use Of Estimates Concentration of Credit Risk and Other Risks and Uncertainties Concentration Risk Credit Risk Cash and Cash Equivalents Cash And Cash Equivalents Policy [Text Block] Marketable Securities Marketable Securities Policy Restricted Cash Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Segments Segment Reporting Policy Policy [Text Block] Leases Lessee Leases Policy [Text Block] Revenue Recognition Revenue Recognition Policy [Text Block] Comprehensive Income (Loss) Comprehensive Income Policy Policy [Text Block] Net Income (Loss) per Share Earnings Per Share Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Fair Value Measurements Fair Value Measurement Policy Policy [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] Summary of Cash Equivalents and Marketable Securities Schedule Of Cash Cash Equivalents And Short Term Investments Table [Text Block] Summary of Reconciliation of Cash, Cash Equivalents, and Restricted Cash Schedule Of Cash And Cash Equivalents Table [Text Block] Summary of Property and Equipment Property Plant And Equipment [Text Block] Schedule of prepaid expenses and other current assets. Summary of Prepaid Expenses and Other Current Assets Schedule Of Prepaid Expenses And Other Current Assets Table [Text Block] Summary of Future Lease Payments for Periods Presented to Operating Lease Liability Lessee Operating Lease Liability Maturity Table [Text Block] Summary of Stock Option Activity 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] Summary of Common Stock Equivalents Excluded Used in Computation of Diluted Net Loss Per Share Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Date of incorporation Entity Incorporation Date Of Incorporation cash, cash equivalents and marketable securities. Summary of significant accounting policies. Summary of significant accounting policies. Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] ASU 842 Accounting Standards Update201602 [Member] Initial Application Period Cumulative Effect Transition Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition Initial Application Period Cumulative Effect Transition [Domain] Adjustments Difference Between Revenue Guidance In Effect Before And After Topic606 [Member] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Cash cash equivalents and marketable securities Cash Cash Equivalents And Marketable Securities Restricted cash Restricted Cash Number of operating segment Number Of Operating Segments Operating lease right-of-use asset Operating lease liability Operating Lease Liability Deferred rent Deferred Rent Credit Cumulative adjustment to decrease accumulated deficit and deferred revenue Cumulative Translation Adjustment Net Of Tax Period Increase Decrease Revenue recognized from performance obligations satisfied in previous periods Contract With Customer Performance Obligation Satisfied In Previous Period 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] Investment Type Investment Type [Axis] Investments Investment Type Categorization [Member] Cash Equivalents Cash Equivalents [Member] Short-term marketable securities Short Term Investments [Member] Long term investments. Long-term marketable securities Long Term Investments [Member] Fair Value Hierarchy and NAV 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] Asset Class Fair Value By Asset Class [Axis] Asset Class Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation By Asset Class [Domain] Money Market Funds Money Market Funds [Member] Corporate Commercial Paper Commercial Paper [Member] Corporate Debt Securities Corporate Debt Securities [Member] Government- sponsored Enterprise Securities U S Government Sponsored Enterprises Debt Securities [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 Assets Fair Value Disclosure Debt Securities Available For Sale [Table] Debt Securities Available For Sale [Table] Cash and Cash Equivalents Cash And Cash Equivalents [Axis] Cash and Cash Equivalents Restricted Cash And Cash Equivalents Cash And Cash Equivalents [Member] Government- sponsored Enterprise Securities U S Government Corporations And Agencies Securities [Member] Financial Instrument Financial Instrument [Axis] Financial Instruments Transfers And Servicing Of Financial Instruments Types Of Financial Instruments [Domain] Schedule Of Available For Sale Securities [Line Items] Schedule Of Available For Sale Securities [Line Items] Amortized Cost, Total Available For Sale Debt Securities Amortized Cost Basis Unrealized Gains, Total Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax Unrealized Losses, Total Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax Fair Value, Total Available For Sale Securities Debt Securities Long term marketable securities contractual maturities period. Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Statistical Measurement Range [Axis] Statistical Measurement Range [Member] Maximum Maximum [Member] Minimum [Member] Minimum [Member] Sales of available-for-sale marketable securities Proceeds From Sale Of Available For Sale Securities Debt Marketable securities in unrealized loss positions Debt Securities Available For Sale Unrealized Loss Position Other than temporary impairments Other Than Temporary Impairment Loss Debt Securities Available For Sale Remaining contractual maturities of long-term marketable securities Long Term Marketable Securities Contractual Maturities Period Aggregate unrealized losses of marketable securities Marketable Securities Unrealized Gain Loss Number of investment positions of marketable securities Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 Aggregate net unrealized gains of marketable securities Marketable Securities Gain Loss Gross proceeds from sales of short-term and long-term marketable securities Realized net gain of marketable securities Marketable Securities Realized Gain Loss Cash And Cash Equivalents [Abstract] Restricted cash, current Restricted Cash Current Restricted cash, non-current Total 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] Laboratory Equipment Equipment [Member] Computer Equipment Computer Equipment [Member] Furniture and Fixtures Furniture And Fixtures [Member] Leasehold Improvements Leasehold Improvements [Member] Property Plant And Equipment [Line Items] Property Plant And Equipment [Line Items] Property and equipment, gross Property Plant And Equipment Gross Less accumulated depreciation and amortization Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Total Prepaid Expense And Other Assets Current [Abstract] Other accounts receivable Accounts And Other Receivables Net Current Prepaid expenses Prepaid Expense Current Total 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] Sanofi agreement. Sanofi Agreement Sanofi Agreement [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 development milestones. Clinical Development Milestones Clinical Development Milestones [Member] AbbVie agreement. AbbVie Agreement Abb Vie Agreement [Member] ASC 605 Calculated Under Revenue Guidance In Effect Before Topic606 [Member] University of California, San Francisco. University Of California San Francisco University Of California San Francisco [Member] Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] IPO I P O [Member] Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Payment received Proceeds From Collaborators License agreement milestone payment upon regulatory milestones and commercial milestones. Royalty payment obligations expiration period. License agreement milestone payment receive regulatory milestones and commercial milestones License Agreement Milestone Payment Upon Regulatory Milestones And Commercial Milestones Royalty expiration period Royalty Payment Obligations Expiration Period Upfront payment recognized. Aggregate milestone payment. Upfront payment recognized Upfront Payment Recognized Aggregate milestone payments Aggregate Milestone Payment Transaction price. Milestone payment. Increase (decrease) in transaction price. Transaction price determined Transaction Price Milestone payments Milestone Payment Revenue recognized Contract With Customer Liability Revenue Recognized Increase in transaction price Increase Decrease In Transaction Price Deferred revenue Deferred Revenue Current Research and development period. Extension of research and development period. Increase (decrease) in accumulated deficit. Research and development period Research And Development Period Extension of research and development period Extension Of Research And Development Period Decrease in accumulated deficit Increase Decrease In Accumulated Deficit Decrease in deferred revenue Increase Decrease In Deferred Revenue Licensing fees. Annual licenses maintenance fee. Licensing fees Licensing Fees Annual licenses maintenance fee Annual Licenses Maintenance Fee Operating leases area under lease. Additional tenant improvement allowance. Lease occupancy commencement date. Commitments and contingencies. Loss Contingencies [Table] Loss Contingencies [Table] Lease Arrangement, Type Lease Arrangement Type [Axis] Lease Arrangement, Type Lease Arrangement Type [Domain] April 2018 lease agreement. April 2018 Lease Agreement April Two Thousand And Eighteen Lease Agreement [Member] Loss Contingency Nature Loss Contingencies By Nature Of Contingency [Axis] Loss Contingency, Nature Loss Contingency Nature [Domain] Indemnification Guarantee Indemnification Guarantee [Member] Commitments And Contingencies [Line Items] Commitments And Contingencies [Line Items] Area under lease Operating Leases Area Under Lease Commencement date Lease Occupancy Commencement Date Term of lease agreement Lessee Operating Lease Term Of Contract Option to extend period Lessee Operating Lease Renewal Term Letter of credit Line Of Credit Tenant improvement Tenant Improvements Additional tenant improvement allowance Additional Tenant Improvement Allowance Operating lease ROU asset Operating lease liability Deferred rent Lessee, operating lease, remaining lease term. Remaining lease terms Lessee Operating Lease Remaining Lease Term Present value of remaining lease payments discount rate Lessee Operating Lease Discount Rate Cash paid for amounts included in measurement of lease liability included in net cash used in operating activities Operating Lease Payments Lease agreement commencement date. Rent expense Operating Lease Expense Lease agreement commencement date Lease Agreement Commencement Date 2020 (remaining 9 months) Lessee Operating Lease Liability Payments Remainder Of Fiscal Year 2021 Lessee Operating Lease Liability Payments Due Year Two 2022 Lessee Operating Lease Liability Payments Due Year Three 2023 Lessee Operating Lease Liability Payments Due Year Four 2024 Lessee Operating Lease Liability Payments Due Year Five 2025 and beyond Lessee Operating Lease Liability Payments Due After Year Five Total lease payments Lessee Operating Lease Liability Payments Due Present value adjustment Lessee Operating Lease Liability Undiscounted Excess Amount Operating lease liability Lease expiration date Lease Expiration Date1 Accruals for expenses related to indemnification issues Loss Contingency Accrual Carrying Value Current Options Outstanding, Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Options Outstanding, Options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross Options Outstanding, Options forfeited Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period Options Outstanding, Options exercised Stock Issued During Period Shares Stock Options Exercised Options Outstanding, Ending Balance Options Outstanding, Vested and expected to vest Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number Options Outstanding, Exercisable as of March 31, 2020 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Weighted Average Exercise Price, Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Weighted Average Exercise Price, Options granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Weighted Average Exercise Price, Options forfeited Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price Weighted Average Exercise Price, Options exercised Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price Weighted Average Exercise Price, Ending Balance Weighted Average Exercise Price, 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 Weighted Average Exercise Price, Exercisable as of March 31, 2020 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Share based compensation arrangement by share based payments award shares subject to repurchase in event of employment termination. Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Exercise Price Range Share Based Compensation Shares Authorized Under Stock Option Plans By Exercise Price Range [Axis] Exercise Price Range Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Domain] Early exercised stock options. Early Exercised Stock Options Early Exercised Stock Options [Member] Award Type Award Type [Axis] Award Type Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Stock Option Employee Stock Option [Member] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Shares repurchase in the event of employment termination Share Based Compensation Arrangement By Share Based Payments Award Shares Subject To Repurchase In Event Of Employment Termination Unvested stock options liabilities Deferred Compensation Share Based Arrangements Liability Current Options vesting period Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 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 Stock Purchase Plan Employee Stock [Member] Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] Two thousand and eighteen and two thousand and eight equity incentive plans. 2018 Equity Incentive Plan/2008 Equity Incentive Plan Two Thousand And Eighteen And Two Thousand And Eight Equity Incentive Plans [Member] Stock-based compensation expense Allocated Share Based Compensation Expense Unamortized compensation cost related to stock awards Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Expected weighted average period Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 Weighted-average remaining contractual term options outstanding Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Antidilutive Securities, Name Antidilutive Securities Name [Domain] Warrants to purchase common stock. Warrants To Purchase Common Stock Warrants To Purchase Common Stock [Member] Common stock options issued and outstanding. Common Stock Options Issued and Outstanding Common Stock Options Issued And Outstanding [Member] Early exercised common stock subject to future vesting. Early Exercised Common Stock Subject To Future Vesting Early Exercised Common Stock Subject To Future Vesting [Member] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Anti-dilutive securities excluded from computation of diluted net loss per share Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount