License And Collaboration Agreements [Line Items] License and Collaboration Agreements [Line Items] License and collaboration agreements. Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Statistical Measurement [Domain] Statistical Measurement [Domain] Summary of Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Our Cash, Cash Equivalents and Marketable Securities Debt Securities, Available-for-Sale [Table Text Block] Award Timing Predetermined Award Timing Predetermined [Flag] Related Party Transaction [Axis] Related Party Transaction [Axis] Entity File Number Entity File Number Tabular List, Table Tabular List [Table Text Block] Leases [Abstract] Leases [Abstract] Cash Cash Equivalents and Investments in Marketable Securities Cash Cash Equivalents And Investments In Marketable Securities [Member] Cash, cash equivalents and investments in marketable securities. Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Accounts payable (($13) and $— to a related party) Accounts payable Increase (Decrease) in Accounts Payable Debt Instrument, Tranche Type [Axis] Debt Instrument, Tranche Type [Axis] Debt Instrument, Tranche Type Receivable from collaboration partners Contract with Customer, Asset, after Allowance for Credit Loss, Current Common stock options issued and outstanding Share-Based Payment Arrangement [Member] License License [Member] Unrealized Loss Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Net loss per share, basic (in dollars per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Related Party - Gilead Sciences, Inc. Related Party Transactions Disclosure [Text Block] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Revenues Revenue from Contract with Customer [Text Block] Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Gilead Collaboration Gilead Collaboration [Member] Gilead Collaboration Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax Summary of Segment Reporting Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Summary of Fair Values of Our Cash, Cash Equivalents and Marketable Securities Cash, Cash Equivalent, and Investment [Table Text Block] Total transaction price Revenue, Remaining Performance Obligation, Amount Adjustment to Compensation, Amount Adjustment to Compensation Amount Percentage of revenues Concentration Risk, Percentage Total revenues from collaborations Revenue from Collaborative Arrangement, Excluding Revenue from Contract with Customer Unamortized discounts, issuance costs, charges and payment-in-kind interest, net Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Consolidation Consolidation, Policy [Policy Text Block] Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Option payment upon completion of certain IND-enabling activities Option Payment Upon Completion Of certain IND-enabling Activities Option payment upon completion of certain IND-enabling activities. Antidilutive Securities Antidilutive Securities [Axis] Total stockholders’ equity Beginning balance Ending balance Equity, Attributable to Parent Debt Securities, Available-for-Sale [Table] Debt Securities, Available-for-Sale [Table] Insider Trading Policies and Procedures [Line Items] Total stock-based compensation Share-Based Payment Arrangement, Expense Common stock, shares authorized (in shares) Common Stock, Shares Authorized Segment Reporting, Asset Reconciling Item [Line Items] Segment Reporting, Asset Reconciling Item [Line Items] Issuance of common stock (in shares) Stock Issued During Period, Shares, New Issues Current assets: Assets, Current [Abstract] Total liabilities and stockholders’ equity Liabilities and Equity Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Accrued research and development Accrued Research And Development Expenses Current Accrued research and development expenses current. Number of board members Number Of Board Members Number Of Board Members Cash, cash equivalents and restricted cash at beginning of period Cash, cash equivalents and restricted cash at end of period Total cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation Non-operating income (expense): Other Nonoperating Income (Expense) [Abstract] Cover [Abstract] Cover [Abstract] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Maximum Maximum [Member] General and administrative General and Administrative Expense [Member] Accounting Policies [Abstract] Accounting Policies [Abstract] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Option continuation payment due upon fourth anniversary of agreement Option Continuation Payment Due Upon Fourth Anniversary Of Agreement Option continuation payment due upon Fourth anniversary of agreement. Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Removal of option continuation payment under agreement Remove Option Continuation Payment Under Agreement Remove option continuation payment under agreement. Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities [Abstract] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Loss before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Other noncurrent liabilities Other Liabilities, Noncurrent Schedule of Long-Term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] STAR-221 Development Activities STAR-221 Development Activities [Member] STAR-221 Development Activities Proceeds from maturities of marketable securities Proceeds From Maturity Of Marketable Securities Proceeds from maturity of marketable securities. Early-stage development and preclinical programs Early Stage Development And Preclinical Programs Early Stage Development And Preclinical Programs Total upfront cash payment Total Upfront Cash Payment Total Upfront Cash Payment Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis Fair Value Assets and Liabilities Measured On Recurring Basis [Table Text Block] Fair value assets and liabilities measured on recurring basis. Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Other liabilities Increase (Decrease) in Other Noncurrent Liabilities Comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent STAR-121 Development Activities STAR-121 Development Activities [Member] STAR-121 Development Activities Name Measure Name Restricted Cash, Noncurrent, Statement of Financial Position [Extensible Enumeration] Restricted Cash, Noncurrent, Statement of Financial Position [Extensible Enumeration] Summary of Stock-Based Compensation Expense Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Secured Debt Secured Debt [Member] Current portion of lease liabilities Operating Lease, Liability, Current AstraZeneca Agreement Astra Zeneca Agreement [Member] AstraZeneca Agreement. Class of Stock [Line Items] Class of Stock [Line Items] Rights to certain studies Rights To Certain Studies [Member] Rights To Certain Studies Document Fiscal Period Focus Document Fiscal Period Focus Cash, Cash Equivalents and Marketable Securities [Abstract] Cash, Cash Equivalents and Marketable Securities [Abstract] Cash, cash equivalents and marketable securities. Gilead Collaboration Agreement Option License And Collaboration Agreement [Member] Option, license and collaboration agreement. Award Timing Method Award Timing Method [Text Block] Development services Development Services [Member] Development Services Award Type Award Type [Axis] Deferred revenue, noncurrent ($36 and $43 to a related party) Deferred revenue, noncurrent Contract with Customer, Liability, Noncurrent Long-term debt Total long-term debt Long-Term Debt Legal Entity [Axis] Legal Entity [Axis] Access rights Access Rights [Member] Access Rights Option continuation payment due upon second anniversary of agreement Option Continuation Payment Due Upon Second Anniversary Of Agreement Option continuation payment due upon second anniversary of agreement. Total assets Assets Assets Trading Symbol Trading Symbol Taiho Pharmaceutical Co., Ltd Taiho Pharmaceutical Co Ltd [Member] Taiho Pharmaceutical Co., Ltd. Option continuation payment due upon sixth anniversary of agreement Option Continuation Payment Due Upon Sixth Anniversary Of Agreement Option continuation payment due upon Sixth anniversary of agreement. Additional clinical, regulatory and commercialization milestone payments Additional Clinical Regulatory And Commercialization Milestone Payments Additional clinical regulatory and commercialization milestone payments. Entity Address, City or Town Entity Address, City or Town Cash flows from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Other segment items Segment Reporting, Other Segment Item, Amount Concentration Risk Type [Axis] Concentration Risk Type [Axis] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Restricted stock units issued Restricted Stock Units (RSUs) [Member] Statement of Income Location, Balance [Domain] Statement of Income Location, Balance [Domain] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Number of programs, eligible to receive regulatory and commercial milestone payments Number Of Programs, Eligible To Receive Regulatory And Commercial Milestone Payments Number of programs, eligible to receive regulatory and commercial milestone payments. Entity Emerging Growth Company Entity Emerging Growth Company Development cost recorded within research and development expenses Research and Development Expense (Excluding Acquired in Process Cost) Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Debt Securities, Available-for-Sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Corporate securities and commercial paper Corporate Securities And Commercial Paper [Member] Corporate securities and commercial paper. Related Party Related Party [Member] Common stock, shares outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding anti-PD-1 Anti P D One [Member] Anti PD one. Plan Name [Axis] Plan Name [Axis] PEO PEO [Member] Proceeds from issuance of secured debt Proceeds from Issuance of Secured Debt Upfront cash payment Upfront Cash Payment Upfront cash payment. Summary of Revenues by Collaboration, Category of Revenue and Method of Recognition Disaggregation of Revenue [Table Text Block] Regulatory and commercial milestone payments received Regulatory And Commercial Milestone Payments Received Regulatory and commercial milestone payments received. Debt instrument, milestone achievement period Debt Instrument, Milestone Achievement Period Debt Instrument, Milestone Achievement Period Changes in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Contract with customer, liability, cumulative catch-up adjustment to revenue, change in measure of progress and change in estimate of transaction price Contract With Customer, Liability, Cumulative Catch-up Adjustment To Revenue, Change In Measure Of Progress And Change In Estimate Of Transaction Price Contract With Customer, Liability, Cumulative Catch-up Adjustment To Revenue, Change In Measure Of Progress And Change In Estimate Of Transaction Price Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Accumulated deficit Retained Earnings [Member] Prepaid expenses and other current assets Total prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Debt instrument, interest rate, effective percentage Debt Instrument, Interest Rate, Effective Percentage Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Share-Based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Income Statement [Abstract] Income Statement [Abstract] Income tax expense Income Tax Expense (Benefit) Purchases of marketable securities Payments to Acquire Marketable Securities Tranche Two Tranche Two [Member] Tranche Two Income taxes payable Taxes Payable, Current Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Product and Service Product and Service [Domain] Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Axis] Customer Concentration Risk Customer Concentration Risk [Member] Current and future programs exclusive access period Current And Future Programs Exclusive Access Period Current and future programs exclusive access period. Reimbursement from related party for shared costs Related Party Transaction Reimbursement From Related Party For Shared Costs Related party transaction reimbursement from related party for shared costs. Cash, cash equivalents, and short-term investments Cash, Cash Equivalents, and Short-Term Investments Net loss Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Cash paid for amounts included in measurement of lease liabilities Cash Paid For Amounts Included In Measurement Of Lease Liabilities Cash paid for amounts included in measurement of lease liabilities. Noncash lease expense Operating Lease, Right-of-Use Asset, Periodic Reduction Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Clinical, regulatory and commercialization milestone payments Clinical Regulatory And Commercialization Milestone Payments Clinical regulatory and commercialization milestone payments. City Area Code City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] License And Collaboration Agreements [Table] License and Collaboration Agreements [Table] License and collaboration agreements. Summary of Transaction Price and Allocation of Transaction Price to the Performance Obligations Schedule Of Transaction Price And Allocated To Transaction Price To Performance Obligations [Table Text Block] Schedule of transaction price and allocated to transaction price to performance obligations. Tranche One Tranche One [Member] Tranche One Summary of Revenue Recognized as a Result of Changes in Deferred Revenue Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] General and administrative (Includes $— and $— from a related party) General and administrative expense General and Administrative Expense Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Net cash used in operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Related Party Transactions [Abstract] Related Party Transactions [Abstract] Subsequent event Subsequent Event [Member] Additional clinical and regulatory milestone payments receivable Additional Clinical And Milestone Payments Received Under License Agreement Additional clinical and milestone payments received under license agreement. Other liabilities Other Liabilities Number of research programs Number Of Research Programs Number of research programs. Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] R&D services R&D Services [Member] R&D Services PEO Total Compensation Amount PEO Total Compensation Amount Long-Term Debt, Type [Axis] Long-Term Debt, Type [Axis] Interest and other income, net Interest and Other Income Expense Nonoperating Net Interest and other income (expense) nonoperating net. Money market funds Money Market Funds [Member] Late-stage development programs Late Stage Development Programs Late Stage Development Programs Taiho Collaboration Agreement Taiho Collaboration Agreement [Member] Taiho Collaboration Agreement Equity Components Equity Components [Axis] Organization, Liquidity and Capital Resources Nature of Operations [Text Block] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Cash and investments Investments and Cash Amended Gilead Collaboration Agreement Amended Gilead Collaboration Agreement [Member] Amended gilead collaboration agreement. Number of reportable segments Number of Reportable Segments Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost Other Performance Measure, Amount Other Performance Measure, Amount Summary of Cash, Cash Equivalents and Restricted Cash Restrictions on Cash and Cash Equivalents [Table Text Block] Entity Address, State or Province Entity Address, State or Province Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Related Party [Domain] Related and Nonrelated Parties [Domain] Total current liabilities Liabilities, Current Reportable segment Reportable Segment [Member] Reportable Segment Individual: Individual [Axis] Research and Development Research and development Research and Development Expense [Member] Entity [Domain] Entity [Domain] Net cash provided by investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Document Fiscal Year Focus Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Entity Interactive Data Current Entity Interactive Data Current Plan Name [Domain] Plan Name [Domain] Other Other Services [Member] Other Services Adjusted for expense (income): Segment Reconciliation [Abstract] Business Segment Segment Reporting Disclosure [Text Block] 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] U.S. treasury securities US Treasury Securities [Member] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Milestone payments Milestone Payments Milestone payments. Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Contingent milestone payments receivable Contingent Milestone Payments Receivable Contingent milestone payments receivable. Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Depreciation and amortization Depreciation, Depletion and Amortization Other noncurrent assets Other Assets, Noncurrent Entity Central Index Key Entity Central Index Key PEO Name PEO Name Total revenues Revenue Total revenues Revenues Sale of stock, consideration received on transaction Sale of Stock, Consideration Received on Transaction Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Arrangement Duration Trading Arrangement Duration WuXi Biologics License Agreement Wu Xi Biologics License Agreement [Member] WuXi Biologics license agreement. Deferred revenue ($27 and $35 to a related party) Deferred revenue, current Contract with Customer, Liability, Current Segments [Axis] Segments [Axis] Exercise Price Award Exercise Price Access right and option continuation periods Access Rights And Option Continuation Periods [Member] Access Rights And Option Continuation Periods Entity Filer Category Entity Filer Category Local Phone Number Local Phone Number Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Collaborative Arrangement and Arrangement Other than Collaborative Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Other items, net Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item Subsequent Event Type [Axis] Subsequent Event Type [Axis] Stock-Based Compensation Share-Based Payment Arrangement [Text Block] Non refundable and non creditable cash payments Non Refundable And Non Creditable Cash Payments Non refundable and non creditable cash payments. ASSETS Assets [Abstract] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Statement of Financial Position Location, Balance [Axis] Statement of Financial Position Location, Balance [Axis] Debt Instrument [Axis] Debt Instrument [Axis] Fair Value Measurements Fair Value Disclosures [Text Block] Stockholders’ equity: Equity, Attributable to Parent [Abstract] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Entity Address, Address Line One Entity Address, Address Line One Research and development (Includes $— and ($5) from a related party) Research and Development Expense Accumulated other comprehensive loss AOCI Attributable to Parent [Member] Balance Sheet Related Disclosures [Abstract] Balance Sheet Related Disclosures [Abstract] Juan Jaen [Member] Juan Jaen Development milestone expense Milestone Expense Milestone expense. Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Other assets Increase (Decrease) in Other Noncurrent Assets Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Compensation and personnel costs Labor and Related Expense Summary of Long-Term Debt Instruments Schedule of Long-Term Debt Instruments [Table Text Block] Number of exercise option to programs Number Of Exercise Option To Programs Number of exercise option to programs. Related Party Transaction [Line Items] Related Party Transaction [Line Items] Option continuation payment receivable upon sixth anniversary of agreement Option Continuation Payment Receivable Upon Sixth Anniversary Of Agreement Option continuation payment receivable upon sixth anniversary of agreement. Document Quarterly Report Document Quarterly Report Total assets measured at fair value Assets, Fair Value Disclosure Payment for option exercise Payment For Option Exercise Payment for option exercise. Number of positions in securities in unrealized loss Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions Collaboration term for current and future clinical programs Collaboration Term For Current And Future Clinical Programs Collaboration term for current and future clinical programs. Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Accrued interest receivable Interest Receivable, Current Counterparty Name [Domain] Counterparty Name [Domain] Number of operating segments Number of Operating Segments Amortization of discounts on marketable securities Accretion (Amortization) of Discounts and Premiums, Investments Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Related Party [Axis] Related and Nonrelated Parties [Axis] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Collaborative Arrangement and Arrangement Other than Collaborative Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Restatement Determination Date: Restatement Determination Date [Axis] Non-PEO NEO Non-PEO NEO [Member] Partnership reimbursements Partnership Reimbursements Partnership Reimbursements Summary of Prepaid and Other Current Assets Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block] Interest expense, debt Interest Expense, Debt Unrealized Gain Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Name Trading Arrangement, Individual Name All Award Types Award Type [Domain] Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Compensation Amount Outstanding Recovery Compensation Amount Debt instrument, face amount Debt Instrument, Face Amount Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Certificate of deposit Certificates of Deposit [Member] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Revenue recognized from amounts in deferred revenue at the beginning of the period Contract with Customer, Liability, Revenue Recognized MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Name Awards Close in Time to MNPI Disclosures, Individual Name anti-CD39 Anti C D Thirty Nine [Member] Anti CD thirty nine. Restricted cash (included in Other noncurrent assets) Restricted Cash, Noncurrent Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Employee stock purchase plan shares Employee Stock [Member] Revenues: Revenues [Abstract] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Debt instrument, face amount, contingently available Debt Instrument, Face Amount, Contingently Available Debt Instrument, Face Amount, Contingently Available Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Financial Instruments [Domain] Financial Instruments [Domain] Segments [Domain] Segments [Domain] Statement of Income Location, Balance [Axis] Statement of Income Location, Balance [Axis] Abmuno License Agreement Abmuno License Agreement [Member] Abmuno license agreement. Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Domain] Statement of Financial Position Location, Balance [Domain] Statement of Financial Position Location, Balance [Domain] Minimum Minimum [Member] Deposits for letters of credit Security Deposit R&D Activities for Inflammation Programs Research And Development Activities For Inflammation Programs [Member] Research and development activities for inflammation programs member. Proceeds from sales of marketable securities Proceeds From Sale Of Marketable Securities Proceeds from sale of marketable securities. Company Selected Measure Name Company Selected Measure Name Sale of stock, number of shares acquired in transaction (in shares) Sale Of Stock, Number Of Shares Acquired In Transaction Sale Of Stock, Number Of Shares Acquired In Transaction Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Accounts payable ($11 and $24 to a related party) Accounts payable, current Accounts Payable, Current Gilead Gilead Sciences Inc [Member] Gilead Sciences, Inc. Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] All Executive Categories All Executive Categories [Member] Stockholders' Equity Note [Abstract] Stockholders' Equity Note [Abstract] Common stock and additional paid-in capital: $0.0001 par value per share; 400.0 shares authorized; 125.5 shares in 2026 and 125.3 shares in 2025 issued and outstanding Common Stock, Value, Issued Hercules Agreement Hercules Agreement [Member] Hercules Agreement Payment for option exercise Payment For Options Exercised Payment for option exercise. Shares used to compute net loss per share, diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Commitments Commitments and Contingencies Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Reconciliation of Assets from Segment to Consolidated [Table] Reconciliation of Assets from Segment to Consolidated [Table] Entity Small Business Entity Small Business Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Long-Term Debt Long-Term Debt [Text Block] Document Transition Report Document Transition Report Underlying Securities Award Underlying Securities Amount Equity Component Equity Component [Domain] Document Period End Date Document Period End Date Option period Option Period Option period. PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Cash, Cash Equivalents and Marketable Securities Cash, Cash Equivalent, and Marketable Security [Text Block] Income Taxes Income Tax Disclosure [Text Block] Condensed Consolidated Balance Sheet Components Supplemental Balance Sheet Disclosures [Text Block] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Robert C. Goeltz II [Member] Robert C. Goeltz II Document Type Document Type Level 3 Fair Value, Inputs, Level 3 [Member] Net Loss Per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Product and Service Product and Service [Axis] Proceeds from issuance of common stock ($— and $14 from a related party) Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Research and development expense, net of recoveries Research And Development Expense, Recoveries Research And Development Expense, Recoveries Total revenues Total revenues from a customer Revenue from Contract with Customer, Excluding Assessed Tax All Individuals All Individuals [Member] Long-Term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Name Forgone Recovery, Individual Name Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Proceeds from issuance of common stock pursuant to equity award plans Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Percentage of outstanding common stock held Percentage Of Outstanding Common Stock Owned Percentage of outstanding common stock owned. Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Current liabilities: Liabilities, Current [Abstract] Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Total operating expenses Operating Expenses Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Other collaboration Other collaboration Other Collaboration Revenue [Member] Other Collaboration Revenue [Member] Level 1 Fair Value, Inputs, Level 1 [Member] Jennifer Jarrett [Member] Jennifer Jarrett Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Schedule Of Related Party Transactions By Related Party [Table] Related Party Transaction [Table] Net loss per share, diluted (in dollars per share) Earnings Per Share, Diluted Equity Award Programs Equity Award Programs [Member] Equity Award Programs [Member] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Title of 12(b) Security Title of 12(b) Security Sale of stock, number of shares issued in transaction (in shares) Sale of Stock, Number of Shares Issued in Transaction Organization [Table] Organization [Table] Organization Earnings Per Share [Abstract] Total non-operating income, net Nonoperating Income (Expense) Summary of Outstanding Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Marketable securities Debt Securities, Available-for-Sale, Current Deferred revenue (($15) and ($28) to a related party) Deferred revenue Increase (Decrease) in Contract with Customer, Liability Potential regulatory approval milestones payment receivable related to domvanalimab Potential Regulatory Approval Milestones Payment Receivable Related To Domvanalimab Potential regulatory approval milestones payment receivable related to domvanalimab. License and development services License And Development Services [Member] License And Development Services Purchase Agreement Common Stock Purchase Agreement [Member] Common stock purchase agreement. Award Timing Disclosures [Line Items] Clinical regulatory milestone payments Clinical Regulatory Milestone Payments Clinical Regulatory Milestone Payments Long-term debt (Contractual maturity 2030) Long-Term Debt, Gross Accrued personnel expenses Employee-related Liabilities, Current Stockholders' Equity Equity [Text Block] Summary of Other Current Liabilities Other Current Liabilities [Table Text Block] Net loss Net loss Net loss Net Income (Loss) Attributable to Parent Expiration Date Trading Arrangement Expiration Date Timing of Transfer of Good or Service [Axis] Timing of Transfer of Good or Service [Axis] Property and equipment, net Property, Plant and Equipment, Net Adoption Date Trading Arrangement Adoption Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Entity Current Reporting Status Entity Current Reporting Status Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Loss from operations Operating Income (Loss) Accumulated deficit Retained Earnings (Accumulated Deficit) Total cash, cash equivalents and marketable securities Cash Cash Equivalents And Available For Sale Investments Cash, cash equivalents and available for sale investments. Financial Instrument [Axis] Financial Instrument [Axis] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] Over time Transferred over Time [Member] Option continuation payment due upon eighth anniversary of agreement Option Continuation Payment Due Upon Eighth Anniversary Of Agreement Option continuation payment due upon Eighth anniversary of agreement. Current Fiscal Year End Date Current Fiscal Year End Date Subsequent Event Type [Domain] Subsequent Event Type [Domain] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Statement [Table] Statement [Table] License And Collaboration Agreements [Abstract] License and Collaboration Agreements [Abstract] License and collaboration agreements. Adjustments to reconcile net loss to net cash used in operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] License and Collaborations Collaborative Arrangement Disclosure [Text Block] Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Revenue Benchmark Revenue Benchmark [Member] Contract with customer, liability Contract with Customer, Liability Debt Instrument, Tranche Type [Domain] Debt Instrument, Tranche Type [Domain] Debt Instrument, Tranche Type [Domain] Option payment upon achievement of certain development milestones Option Payment Upon Achievement Of Certain Development Milestones Option payment upon achievement of certain development milestones. Timing of Transfer of Good or Service [Domain] Timing of Transfer of Good or Service [Domain] Antidilutive securities excluded from computation of diluted net loss per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount All Adjustments to Compensation All Adjustments to Compensation [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Amendment Flag Amendment Flag Sale of stock, price per share (in dollars per share) Sale of Stock, Price Per Share Summary of Cash and Non-cash Information Related to Operating Leases Schedule Of Supplemental Cash Flow Disclosures And Non-Cash Financing Activities Related To Operating Leases [Table Text Block] Schedule of supplemental cash flow disclosures and non-cash financing activities related to operating leases. Leases Lessee, Operating Leases [Text Block] Termination Date Trading Arrangement Termination Date Net cash provided by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Receivable from collaboration partners ($— and $2 from a related party) Receivable from collaboration partners Increase (Decrease) in Contract with Customer, Asset Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] Credit related losses Financing Receivable, Credit Loss, Expense (Reversal) Long-term marketable securities Debt Securities, Available-for-Sale, Noncurrent Taiho Agreement Option And License Agreement [Member] Option and license agreement. Shares used to compute net loss per share, basic (in shares) Weighted Average Number of Shares Outstanding, Basic Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Related Party Transaction [Domain] Related Party Transaction [Domain] Segment Reporting [Abstract] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Debt Disclosure [Abstract] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Common stock and additional paid-in capital Common Stock Including Additional Paid in Capital [Member] Entity Tax Identification Number Entity Tax Identification Number Debt Instrument, additional committed amount Debt Instrument, Additional Committed Amount Debt Instrument, Additional Committed Amount Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Option fee per program for all other programs entering clinical development to exercise option Option Fee Per Program For All Other Programs Entering Clinical Development To Exercise Option Option fee per program for all other programs entering clinical development to exercise option. Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares issued (in shares) Common Stock, Shares, Issued Use of Estimates Use of Estimates, Policy [Policy Text Block] Interest expense Interest income, net Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Total Shareholder Return Amount Total Shareholder Return Amount Insider Trading Arrangements [Line Items] Security Exchange Name Security Exchange Name Antidilutive Securities, Name Antidilutive Securities, Name [Domain] Royalties payable term Royalties Payable Term Royalties Payable Term Reimbursement of research and development expense Reimbursement Of Research And Development Expense Reimbursement of research and development expense Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Operating expenses: Operating Expenses [Abstract] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Prepaid expenses and other assets Prepaid Expenses And Other Current Assets Prepaid expenses and other current assets. Taiho Collaboration Taiho Collaboration [Member] Taiho Collaboration Other current liabilities Total other current liabilities Other Liabilities, Current Other Other Sundry Liabilities, Current Issuance of common stock Stock Issued During Period, Value, New Issues Statement [Line Items] Statement [Line Items] Deferred revenue, non-refundable payment Deferred Revenue, Non-Refundable Payment Deferred Revenue, Non-Refundable Payment Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and Cash Equivalent Option payments received Option Payment Received Option payment received. Organization [Line Items] Organization [Line Items] Organization [Line Items] Counterparty Name [Axis] Counterparty Name [Axis] Common stock Common Stock [Member] Fair Value Debt Securities, Available-for-Sale Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Net increase (decrease) in cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation