Revision of Prior Period [Axis] Revision of Prior Period [Axis] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Total undiscounted lease payments Lessee, Operating Lease, Liability, to be Paid Schedule of Reconciliation of Cash, Cash Equivalent Schedule of Cash and Cash Equivalents [Table Text Block] Foreign Currency Transactions Foreign Currency Transactions and Translations Policy [Policy Text Block] Net loss Net Income (Loss), Including Portion Attributable to Noncontrolling Interest NGM Biopharmaceuticals NGM Biopharmaceuticals [Member] NGM Biopharmaceuticals Entity Address, Postal Zip Code Entity Address, Postal Zip Code Area of leased property Area of Real Estate Property Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Total property and equipment, gross Property, Plant and Equipment, Gross Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Property Subject to or Available for Operating Lease, by Major Property Class [Table] Property, Plant, and Equipment, Lessor Asset under Operating Lease [Table] Financial Instruments [Domain] Financial Instruments [Domain] Statistical Measurement [Domain] Statistical Measurement [Domain] Depreciation Depreciation expense Depreciation Issuance of common stock upon exercise of stock options (in shares) Options exercised (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Short-Term Debt, Type [Axis] Short-Term Debt, Type [Axis] Operating lease liability Operating Lease, Weighted Average Discount Rate, Percent Proceeds from maturities of marketable securities Proceeds from Sale and Maturity of Marketable Securities Additional paid-in capital Additional Paid in Capital, Common Stock Other non-cash expenses Other Noncash Income (Expense) Amount of fund received for research activities Amount Of Fund Received For Research Activities Amount of fund received for research activities. Funded percentage of global development costs Research And Development Collaboration Agreement, Global Development Costs, Funded Percentage Research And Development Collaboration Agreement, Global Development Costs, Funded Percentage Options to purchase common stock Options To Purchase Common Stock [Member] Options to purchase common stock. Amount of additional fund received for research activities Amount Of Additional Fund Received For Research Activities Amount of additional fund received for research activities Net loss Net loss Net loss Net Income (Loss) Attributable to Parent 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 (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Subsequent Event Type [Axis] Subsequent Event Type [Axis] Equity Component Equity Component [Domain] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Scenario [Axis] Scenario [Axis] Ownership [Axis] Ownership [Axis] Fair value of financial assets Assets, Fair Value Disclosure Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Summary of significant accounting policies. Related Party [Domain] Related Party [Domain] Common stock options outstanding Common Stock Options Outstanding [Member] Common stock options outstanding. Fair Value Debt Securities, Available-for-Sale Options cancelled (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Merck Sharp & Dohme Corp Merck Sharp And Dohme Corporation [Member] Merck Sharp and Dohme Corporation. Increase in initial base rent (as a percent) Lessee, Operating Lease, Liability, to be Paid, Increase In Initial Base Rent, Percent Lessee, Operating Lease, Liability, to be Paid, Increase In Initial Base Rent, Percent Number of operating business segment Number of Operating Segments 2022 (remaining) Lessee, Operating Lease, Liability, to be Paid, Remainder of Fiscal Year Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Entity Address, State or Province Entity Address, State or Province Level 1 Fair Value, Inputs, Level 1 [Member] ESPP ESPP shares available for purchase Employee Stock [Member] Weighted Average Remaining Contractual Life (In Years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Award Type [Axis] Award Type [Axis] Net cash used in operating activities Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Operating lease liability, current Operating Lease, Liability, Current Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Related Party Transaction [Domain] Related Party Transaction [Domain] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Legal Entity [Axis] Legal Entity [Axis] Total liabilities Liabilities Weighted average discount rate Operating Lease, Weighted Average Remaining Lease Term Geographical [Axis] Geographical [Axis] Investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Issuance of common stock under offering, net of issuance costs Stock Issued During Period, Value, New Issues Accrued and other liabilities Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Laboratory equipment and office furniture Laboratory Equipment And Office Furniture [Member] Laboratory equipment and office furniture. Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Schedule of Milestone Payments by Indications Collaborative Arrangement and Arrangement Other than Collaborative [Table Text Block] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Property and Equipment Property, Plant and Equipment [Table Text Block] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Document Type Document Type Weighted Average Exercise Price Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Estimated useful life of asset (in years) Property, Plant and Equipment, Useful Life Concentration Risk Benchmark Concentration Risk Benchmark [Domain] Options cancelled (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period Assets: Assets, Fair Value Disclosure [Abstract] Reduction in letter of credit Increase (Decrease) in Deposits Entity Shell Company Entity Shell Company 2023 Lessee, Operating Lease, Liability, to be Paid, Year One Financial Instrument [Axis] Financial Instrument [Axis] Subsequent Event Subsequent Event [Member] Revenue Revenue Benchmark [Member] Document Period End Date Document Period End Date Merck Merck [Member] Merck. Total assets Assets Income Statement Location [Axis] Income Statement Location [Axis] Antidilutive Securities Antidilutive Securities [Axis] Accrued liabilities Accrued Liabilities, Current Options exercised (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Accounting Policies [Abstract] Accounting Policies [Abstract] Personnel-related costs Employee-related Liabilities, Current Variable lease costs Variable Lease, Cost Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Common stock options available for grant Common Stock Options Available For Grant [Member] Common stock options available for grant. Customer Customer [Axis] Balance Sheet Components Supplemental Balance Sheet Disclosures [Text Block] Operating lease liability Increase (Decrease) in Operating Lease Liability Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Short-term marketable securities Short-Term Investments [Member] Award Type [Domain] Award Type [Domain] Exercisable, weighted average remaining contractual life Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Computer equipment Computer Equipment [Member] Entity Registrant Name Entity Registrant Name Issuance of common stock under offering, net of issuance costs (in shares) Stock Issued During Period, Shares, New Issues Manufacturing costs Accrued Manufacturing Costs Accrued Manufacturing costs current. Subsequent Event Subsequent Events [Text Block] Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Summary of significant accounting policies Entity Address, City or Town Entity Address, City or Town Tenant improvement allowances Tenant Improvements 401(k) Matching Plan Four Zero One K Matching Plan [Member] Four zero one k matching plan. Related party receivable from collaboration Increase (Decrease) in Accounts Receivable, Related Parties Operating expenses: Operating Expenses [Abstract] Asset Class [Domain] Asset Class [Domain] Minimum Minimum Minimum [Member] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Common stock, par value (in shares) Common Stock, Par or Stated Value Per Share Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Pension Plan Pension Plan [Member] Fair Value Measurements Fair Value Disclosures [Text Block] Trading Symbol Trading Symbol Entity File Number Entity File Number Revision of Prior Period, Accounting Standards Update, Adjustment Revision of Prior Period, Accounting Standards Update, Adjustment [Member] Research and development Research and Development Expense Title of Individual [Axis] Title of Individual [Axis] Concentration Risk Benchmark Concentration Risk Benchmark [Axis] Related party receivable from collaboration Due from Related Parties, Current Vested and expected to vest (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Use of Estimates Use of Estimates, Policy [Policy Text Block] Other comprehensive (loss) gain, net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Aggregate offering price Sale of Stock, Aggregate Offering Price Sale of Stock, Aggregate Offering Price Clinical Development Event [Axis] Clinical Development Event [Axis] Clinical Development Event Accounts payable Increase (Decrease) in Accounts Payable Subsequent Events [Abstract] Percentage of revenue Concentration Risk, Percentage Income Taxes Income Tax Disclosure [Text Block] Related party revenue Related party revenue Revenue from Related Parties Clinical trials and research and development costs Accrued Clinical Trials And Research And Development Costs Current Accrued clinical trials and research and development costs current. Aggregate intrinsic value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding Credit Facility [Domain] Credit Facility [Domain] Net loss per share, basic (in dollars per share) Earnings Per Share, Basic Schedule of Reconciliation of Restricted Cash Restrictions on Cash and Cash Equivalents [Table Text Block] Concentration Risk Type Concentration Risk Type [Domain] Counterparty Name [Domain] Counterparty Name [Domain] Number of purchase periods Number Of Purchase Periods Number of purchase periods. Total stockholders' equity Beginning balance Ending balance Stockholders' Equity Attributable to Parent Ownership [Domain] Ownership [Domain] Entity Interactive Data Current Entity Interactive Data Current Common stock sold under Sales Agreement Sale of Stock, Number of Shares Issued in Transaction First Indication First Indication [Member] First indication. Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Numerator: Net Income (Loss) Attributable to Parent [Abstract] Money market funds Money Market Funds [Member] Vesting of common stock from early exercises Vesting Of Common Stock From Early Exercises Vesting of common stock from early exercises. Accumulated Deficit Retained Earnings [Member] Total lease cost Lease, Cost Common Stock Common Stock [Member] Maximum percentage of payroll deductions of employee's compensation Share-Based Compensation Arrangement by Share-Based Payment Award, Maximum Employee Subscription Rate Summary of Stock Based Compensation Expense Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Components of Lease Costs Lease, Cost [Table Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Stock options, early exercise, repurchase period Share-Based Compensation Arrangement By Share-based Payment Award, Options, Early Exercise Repurchase Period Share-Based Compensation Arrangement By Share-based Payment Award, Options, Early Exercise Repurchase Period Marketable Securities Marketable Securities, Policy [Policy Text Block] Statement [Table] Statement [Table] Cash, cash equivalents and marketable securities Cash, Cash Equivalents, and Short-Term Investments Operating lease option additional extend term Lessee, Operating Lease, Renewal Term Document Quarterly Report Document Quarterly Report Letter of Credit Letter of Credit [Member] Current assets: Assets, Current [Abstract] Operating lease liability, non-current Operating Lease, Liability, Noncurrent Remaining extension term Research And Development Option Remaining Extension Term Research And Development Option Remaining Extension Term Statistical Measurement [Axis] Statistical Measurement [Axis] Related Party Transaction [Axis] Related Party Transaction [Axis] Leasehold improvements Leasehold Improvements [Member] Percentage of purchase of common stock fair market value Share-Based Compensation Arrangement by Share-Based Payment Award, Discount from Market Price, Offering Date Accumulated deficit Accumulated deficit Retained Earnings (Accumulated Deficit) Purchase of marketable securities Payments to Acquire Marketable Securities Equity Components Equity Components [Axis] Scenario [Domain] Scenario [Domain] Fair Value Measurements, Recurring Fair Value, Recurring [Member] Exercisable, weighted average exercise price (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Segment and Geographical Information Segment Reporting, Policy [Policy Text Block] Comprehensive Loss Comprehensive Income, Policy [Policy Text Block] Revision of Prior Period [Domain] Revision of Prior Period [Domain] Interest income, net Interest Income (Expense), Nonoperating, Net Document Fiscal Year Focus Document Fiscal Year Focus Operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Statement [Line Items] Statement [Line Items] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Proof-Of-Concept Trial, CVM Research Proof-Of-Concept Trial, CVM Research Program [Member] Proof-Of-Concept Trial, CVM Research Program Gross Unrealized Loss Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Operating lease right-of-use asset Operating Lease, Right-of-Use Asset Other Comprehensive Loss AOCI Attributable to Parent [Member] Impairment of Long-Lived Assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Vesting of common stock from early exercises Stock Issued During Period Value Vesting Of Early Exercised Stock Options Stock issued during period value vesting of early exercised stock options. Operating lease, expense Operating Lease, Expense Vested and expected to vest, weighted average exercise price (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Document Transition Report Document Transition Report Local Phone Number Local Phone Number Summary of Activity under 2008 Plan and 2018 Plan Share-Based Payment Arrangement, Option, Activity [Table Text Block] Loss from operations Operating Income (Loss) Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Denominator: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Balance Sheet Related Disclosures [Abstract] Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] 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] Geographical [Domain] Geographical [Domain] Proceeds from Open Market Sale Agreement Proceeds From Issuance Open Market Agreement Proceeds From Issuance Open Market Agreement Collaborative Arrangement and Arrangement Other than Collaborative [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Table] Property and Equipment, Net Property, Plant and Equipment, Policy [Policy Text Block] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Income Statement [Abstract] Income Statement [Abstract] Options granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Additional Paid-In Capital Additional Paid-in Capital [Member] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Document Fiscal Period Focus Document Fiscal Period Focus Restricted cash Restricted cash Restricted Cash, Noncurrent Intrinsic value of stock options exercised Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value Operating Lease, Expense, Term [Axis] Operating Lease, Expense, Term [Axis] Operating Lease, Expense, Term Second Indication Second Indication [Member] Second indication. Cash and Cash Equivalents Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block] Weighted average shares used to compute net loss per share, diluted (in shares) Weighted average number of shares used in computing net loss per share, diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Less: accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Accounting Standards Update and Change in Accounting Principle Accounting Standards Update and Change in Accounting Principle [Table Text Block] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaboration Agreement Collaborative Arrangement [Member] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] 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] Common stock, $0.001 par value; 400,000 shares authorized; 79,463 and 77,962 shares issued and outstanding as of June 30, 2022 and December 31, 2021, respectively Common Stock, Value, Issued Potentially Dilutive Securities Not Included in the Diluted Net Loss Per Share Calculations Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Share of global development costs percentage Share Of Global Development Costs Percentage Share of global development costs percentage. 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] Exercisable, aggregate intrinsic value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value Capitalized Contract Cost [Domain] Capitalized Contract Cost [Domain] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized 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 Equivalents, Restricted Cash, and Restricted Cash Equivalents Reduction in related party contract asset due to Amended Collaboration Agreement with Merck Increase (Decrease) in Due From Related Parties, Contract Assets, Noncash Increase (Decrease) in Due From Related Parties, Contract Assets, Noncash NGM Merck Amended Agreement NGM Merck Amended Agreement [Member] NGM Merck Amended Agreement Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Current liabilities: Liabilities, Current [Abstract] Proceeds from exercise of stock options Proceeds from Stock Options Exercised Common stock, shares issued (in shares) Common Stock, Shares, Issued Vested and expected to vest, weighted average remaining contractual life Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Contract liabilities Contract with Customer, Liability, Current Property and equipment purchases accrued and not yet paid Capital Expenditures Incurred but Not yet Paid Vesting of common stock from early exercises (in shares) Stock Issued During Period Shares Vesting Of Early Exercised Stock Options Stock issued during period shares vesting of early exercised stock options. Retirement Plan Type [Domain] Retirement Plan Type [Domain] Income Statement Location [Domain] Income Statement Location [Domain] 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] Total accrued liabilities Accrued Liabilities Amendment Flag Amendment Flag Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Operating lease costs Operating Lease, Cost Issuance of common stock under employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Total comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Construction-in-progress Construction in Progress [Member] Gross Unrealized Gain Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Entity Current Reporting Status Entity Current Reporting Status Other non-current assets Other Assets, Noncurrent Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract] Exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Letter of credit as a security deposit Security Deposit Japan JAPAN Operating lease term Lessee, Operating Lease, Term of Contract Duration of each purchase period Duration Of Each Purchase Period Duration of each purchase period. Issuance of common stock under employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Option exercise fee Research And Development, Option Exercise Fee Research And Development, Option Exercise Fee Counterparty Name [Axis] Counterparty Name [Axis] Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] Beginning balance (in shares) Ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Research collaboration and license agreements extension fee Research Collaboration And License Agreements Extension Fee Research collaboration and license agreements extension fee. Number of marketable securities in unrealized loss positions less than 12 months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Collaborative Arrangement [Line Items] Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] Basis of Presentation and Principles of Consolidation Basis of Accounting, Policy [Policy Text Block] Property and equipment, net Total property and equipment, net Total leasehold improvements Property, Plant and Equipment, Net Operating lease payment obligations Operating Lease, Payments Title of Individual [Domain] Title of Individual [Domain] Issuance of common stock upon exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Other income (expense), net Other Nonoperating Income (Expense) Research and development performance obligation period Research And Development Performance Obligation Period Research And Development Performance Obligation Period Balance Sheet Location [Axis] Balance Sheet Location [Axis] Net unrealized (loss) gain on available-for-sale marketable securities OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Common stock, shares authorized (in shares) Common Stock, Shares Authorized Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Total operating expenses Operating Expenses Maximum Maximum [Member] Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Remaining extension fee Research Collaboration And License Agreements Remaining Extension Fee Research Collaboration And License Agreements Remaining Extension Fee Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Shares committed under ESPP Share-Based Payment Arrangement [Member] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Contract liabilities Increase (Decrease) in Contract with Customer, Liability Total current assets Assets, Current Monthly base rent Operating Lease, Expense, Monthly Term [Member] Operating Lease, Expense, Monthly Term Entity Small Business Entity Small Business Beginning balance (in shares) Ending balance (in shares) Shares, Outstanding Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Measurement Frequency [Domain] Measurement Frequency [Domain] Non-cash lease expense Noncash lease expense Operating Lease, Right-of-Use Asset, Amortization Expense Third Indication Third Indication [Member] Third indication. Required amount to expend Amount Of Fund Received For Research Activities, Required Expendable Amount Amount Of Fund Received For Research Activities, Required Expendable Amount Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Tenant improvement allowance Lessee, Operating Lease, Tenant Improvement Allowance Lessee, Operating Lease, Tenant Improvement Allowance Number of Options (In Thousands) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Issuance of common stock to participants in 401(k) Plan (in shares) Stock Issued During Period, Shares, Employee Benefit Plan Tax benefits realized Share-Based Payment Arrangement, Expense, Tax Benefit Deferred rent Increase (Decrease) in Prepaid Rent European Union European Union [Member] Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Title of 12(b) Security Title of 12(b) Security Organization and Description of Business Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Ownership interest Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Short-term marketable securities Short-Term Investments Subsequent Event [Line Items] Subsequent Event [Line Items] Class of Stock [Line Items] Class of Stock [Line Items] Present value of lease liabilities Operating Lease, Liability U.S. treasury securities US Government Agencies Debt Securities [Member] Clinical Development Event [Domain] Clinical Development Event [Domain] Clinical Development Event [Domain] Stock-Based Compensation Share-Based Payment Arrangement [Policy Text Block] Amortization of premium on marketable securities Accretion (Amortization) of Discounts and Premiums, Investments Milestone payment for potential achievement of certain clinical development events Milestone Payment For Potential Achievement Of Certain Clinical Development Events Milestone payment for potential achievement of certain clinical development events. Previously Reported Previously Reported [Member] Operating Lease, Expense, Term [Domain] Operating Lease, Expense, Term [Domain] Operating Lease, Expense, Term [Domain] Liabilities and stockholders' equity Liabilities and Equity [Abstract] Options granted (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost Maximum duration for purchase under employee stock purchase plan Offering Period For Purchase Under Employee Stock Purchase Plan Offering period for purchase under employee stock purchase plan. Aggregate net proceeds Sale of Stock, Consideration Received on Transaction Accounts payable Accounts Payable, Current Vested and expected to vest, aggregate intrinsic value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Agreed-upon data package Research And Development Collaboration Agreement, Exercisable Agreed-upon Data Package Research And Development Collaboration Agreement, Exercisable Agreed-upon Data Package Performance of R&D services period Research And Development Service Performance Period Research and development service performance period. Entity Filer Category Entity Filer Category Phase 3 Clinical Event Phase 3 Clinical Event [Member] Phase 3 Clinical Event Proceeds from follow on offering, net Proceeds from Issuance of Common Stock Weighted average shares used to compute net loss per share, basic (in shares) Weighted average number of shares used in computing net loss per share, basic (in shares) Weighted Average Number of Shares Outstanding, Basic United States UNITED STATES Common stock remaining to be sold under open market sales agreement Sale of Stock, Common Stock Available For Issuance Sale of Stock, Common Stock Available For Issuance Total stock-based compensation expense Share-Based Payment Arrangement, Expense Reinvestment amount from option fee Research And Development, Option Exercise Fee, Reinvestment Amount Research And Development, Option Exercise Fee, Reinvestment Amount Supplemental disclosures of non-cash investing and financing activities: Noncash Investing and Financing Items [Abstract] Commitments and contingencies Commitments and Contingencies Security Exchange Name Security Exchange Name Beginning balance (in dollars per share) Ending balance (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Preferred stock, $0.001 par value; 10,000 shares authorized; no shares issued or outstanding as of June 30, 2022 and December 31, 2021, respectively Preferred Stock, Value, Issued Base rent, lease term Operating Lease, Expense, Contract Term [Member] Operating Lease, Expense, Contract Term Letter of credit Letters of Credit Outstanding, Amount Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Short-Term Debt, Type [Domain] Short-Term Debt, Type [Domain] General and administrative General and Administrative Expense [Member] Related party revenue Revenue from Contract with Customer, Excluding Assessed Tax Corporate and agency bonds Corporate Bond Securities [Member] Percentage of contribution matched by employer in common stock Defined Contribution Plan, Employer Matching Contribution, Percent of Match Total (in shares) Common Stock, Capital Shares Reserved for Future Issuance Cash and cash equivalents Cash and Cash Equivalents [Member] Cover [Abstract] Cover [Abstract] Leases Lessee, Leases [Policy Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Related party contract asset Increase (Decrease) in Contract with Customer, Asset Forecast Forecast [Member] Total liabilities and stockholders' equity Liabilities and Equity Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Proceeds from employee stock purchase plan Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Excluding Option Exercised Related Party [Axis] Related Party [Axis] Organization, Consolidation and Presentation of Financial Statements [Abstract] 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Concentration Risk Customer Concentration Risk [Member] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-Sale Securities [Table] Transaction price for the two-year performance obligation Revenue, Remaining Performance Obligation, Amount Corporate and agency bonds Corporate Debt Securities [Member] Lessee, Operating Lease, Liability, Maturity Lessee, Operating Lease, Liability, Maturity [Table Text Block] Entity Address, Address Line One Entity Address, Address Line One Purchases of property and equipment Payments to Acquire Machinery and Equipment Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Merck Original Agreement Merck Original Agreement [Member] Merck Original Agreement Credit Facility [Axis] Credit Facility [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Accrued Liabilities Schedule of Accrued Liabilities [Table Text Block] Capitalized Contract Cost [Axis] Capitalized Contract Cost [Axis] Equity [Abstract] Equity [Abstract] Subsequent Event [Table] Subsequent Event [Table] Entity Tax Identification Number Entity Tax Identification Number Cash on deposit with banks Interest-Bearing Deposits in Banks and Other Financial Institutions Related party contract asset Contract with Customer, Asset, after Allowance for Credit Loss, Current Reserve balance for Sales Agreement Reserve Balance For Sales Agreement [Member] Reserve Balance For Sales Agreement Net decrease in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Issuance of common stock to participants in 401(k) plan Stock Issued During Period, Value, Employee Benefit Plan Commercial paper Commercial paper Commercial Paper [Member] Entity Central Index Key Entity Central Index Key Antidilutive Securities, Name Antidilutive Securities, Name [Domain] Measurement Frequency [Axis] Measurement Frequency [Axis] Research and Development Research and Development Expense, Policy [Policy Text Block] Reimbursable expense Research And Development Reimbursable Expense Research And Development Reimbursable Expense Research Collaboration and License Agreements Collaborative Arrangement Disclosure [Text Block] Concentration of Credit and Other Risks Concentration Risk, Credit Risk, Policy [Policy Text Block] Accrued expenses Other Accrued Liabilities, Current Entity [Domain] Entity [Domain] City Area Code City Area Code General and administrative General and Administrative Expense Assets Assets [Abstract] Merck Amended Agreement Merck Amended Agreement [Member] Merck Amended Agreement Employees and Directors Employees And Directors [Member] Employees and directors. Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Axis] Maximum annual contributions of common stock per employee per year Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount Financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Asset Class [Axis] Asset Class [Axis] Net Loss per Share Earnings Per Share, Policy [Policy Text Block] Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Weighted-average grant date fair value of stock options, granted (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Common stock reserved for future issuance (in shares) Deferred Compensation Arrangement with Individual, Common Stock Reserved for Future Issuance Additional term Research And Development Option Extend Term Research and development option extend term. Research and development Research and Development Expense [Member] Proof-Of-Concept Trial, B7H4 Research Program Proof-Of-Concept Trial, B7H4 Research Program [Member] Proof-Of-Concept Trial, B7H4 Research Program Computation of Net Loss Per Common Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Right of use asset acquired under operating lease on the adoption of ASC 842 Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Milestone payments in connection with potential achievement of certain regulatory events Milestone Payment For Potential Achievement Of Certain Regulatory Events Milestone payment for potential achievement of certain regulatory events. Customer Customer [Domain]