Vesting period Defined Contribution Plan Vesting Period The vesting period for a defined contribution plan. Weighted-average remaining contractual term, options vested and expected to vest Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term 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] Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Option to extend Lessee, Operating Lease, Existence of Option to Extend [true false] Federal statutory income tax Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Cover [Abstract] Cover [Abstract] Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Five Net (decrease) increase in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Schedule of operating lease liabilities maturities Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Income Tax Jurisdiction [Domain] Income Tax Jurisdiction [Domain] Trading Symbol Trading Symbol Less: Net gain recorded on sale of equity securities Equity Securities, FV-NI, Realized Gain (Loss) Comprehensive loss Comprehensive loss attributable to Xencor, Inc. Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Non-NEOs Non-NEOs [Member] (Loss) gain on equity securities, net Change in fair value of equity securities Net gain (loss) recognized on equity securities Net (loss) gain recorded on equity securities Equity Securities, FV-NI, Gain (Loss) Accounts receivable Collaboration Agreement, Accounts Receivable Collaboration Agreement, Accounts Receivable Capitalized research and development costs Deferred Tax Assets, Tax Deferred Expense, Capitalized Research and Experimental Expenditures Deferred Tax Assets, Tax Deferred Expense, Capitalized Research and Experimental Expenditures Net Income (Loss) Per Share Earnings Per Share, Policy [Policy Text Block] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Issuance of restricted stock units (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Award Timing Disclosures [Line Items] Interest income Interest Income (Expense), Operating Patent License Agreement Patent License Agreement Information relating to a Patent License Agreement. Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Collaboration research and licensing agreements Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] Segment Reporting Segment Reporting, Policy [Policy Text Block] Plan Name [Domain] Plan Name [Domain] Other assets Other Assets, Noncurrent Leases [Abstract] Leases [Abstract] Income Taxes [Line Items] Income Taxes [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Amortizable intangible assets Finite-Lived Intangible Assets, Gross Research credits Deferred Tax Assets, Tax Credit Carryforwards, Research Foreign-derived intangible income Effective Income Tax Rate Reconciliation, FDII, Amount Supplier [Domain] Supplier [Domain] Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Operating Activities Non-cash interest expense recognized Royalty Liability, Non-Cash Interest Expense Royalty Liability, Non-Cash Interest Expense Award Timing Method Award Timing Method [Text Block] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Common stock fair value per share minimum (in dollars per share) Share Based Compensation Arrangement By ShareBased Payment Award Fair Value Assumptions Common Stock Fair Value Per Share Minimum The minimum estimated fair value of the entity's common stock at the date of grant of stock options, used as an input in calculating the grant date fair value of the options. Measurement Frequency [Axis] Measurement Frequency [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Insider Trading Policies and Procedures [Line Items] Sales of Future Royalties [Table] Sales of Future Royalties [Table] Sales of Future Royalties [Table] Use of Estimates Use of Estimates, Policy [Policy Text Block] Adjustment to Compensation, Amount Adjustment to Compensation Amount Compensation Amount Outstanding Recovery Compensation Amount 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] Entity Small Business Entity Small Business Company Selected Measure Amount Company Selected Measure Amount Nonrefundable upfront payment Collaborative Arrangement Nonrefundable Upfront Fees Represents the amount of nonrefundable upfront fees as provided under the collaboration agreement. Tabular List, Table Tabular List [Table Text Block] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Stock-based compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-Based Payment Arrangement, Amount Accrued expenses Accrued Liabilities, Current Equity securities without readily determinable fair value Equity Securities without Readily Determinable Fair Value [Line Items] Long-Lived Assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Initial term of plan Share-based Compensation Arrangement by Share-based Payment Award, Initial Term of Plan The initial period of time from the date the plan becomes effective until it expires. Credit Facility [Domain] Credit Facility [Domain] Collaboration agreement, effective rate Collaboration Agreement, Effective Rate Collaboration Agreement, Effective Rate Amounts on deposit in excess of federally insured limits approximately Cash, Uninsured Amount Debt - short-term Royalty Liabilities, Short-Term Debt Royalty Liabilities, Short-Term Debt Finite Lived And Indefinite Lived Intangible Assets By Major Class [Table] Finite Lived And Indefinite Lived Intangible Assets By Major Class [Table] Disclosure of finite-lived and indefinite-lived intangible assets, excluding goodwill, in total and by major class. Stock options Share-Based Payment Arrangement, Option [Member] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] The 2013 Plan The 2013 Plan Represents information pertaining to the 2013 Equity Incentive Plan. 2025 Lessee, Operating Lease, Liability, to be Paid, Year One Licensing License [Member] Comprehensive loss attributable to Xencor, Inc. Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Income tax payable Accrued Income Taxes, Current Omeros Omeros This member stands for Omeros Corporation. Debt of Future Royalties Debt of Future Royalties [Table Text Block] Debt of Future Royalties Schedule of maturities of marketable securities Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of useful lives by asset category Property Plant and Equipment Useful Life [Table Text Block] Tabular disclosure of the useful life of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Award Type [Axis] Award Type [Axis] Schedule of equity securities with readily determinable fair value Equity Securities, FV-NI [Table Text Block] Tabular disclosure of equity securities with readily determinable fair value. Corporate Securities Corporate Debt Securities [Member] Basic and diluted: Earnings Per Share, Basic [Abstract] Annual percentage increase in shares of common stock available for issuance Share Based Compensation Arrangement by Share Based Payment Award Annual Percentage Increase in Shares Authorized Represents the annual percentage increase in maximum number of shares (or other type of equity) approved (usually by shareholders and board of directors), for awards under the equity-based compensation plan. Gale Gale [Member] Gale Milestone Milestone Payment for achievement or success. Property and equipment, net Total property and equipment, net Property, Plant and Equipment, Net ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Total liabilities Liabilities Non-controlling interest Equity, Attributable to Noncontrolling Interest 6% of participating employee contributions 6% of participating employee contributions Represents the third range at which employees' contributions are matched by a employer. Percentage of responsibility for development costs Collaborative Agreement, Percentage of Responsibility Assumed for Development Costs Represents the percentage of responsibility assumed for development costs, if the company elects to participate in development. Weighted-average exercise price per share of exercisable options (in dollars per share) Exercisable (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Expiration Date Trading Arrangement Expiration Date Number of leases Lessee, Operating Lease, Number of Leases Lessee, Operating Lease, Number of Leases Investment owned, balance, shares (in shares) Investment Owned, Balance, Shares Lease liabilities Lease liabilities - short-term Operating Lease, Liability, Current Total Shareholder Return Amount Total Shareholder Return Amount Reconciliation of federal statutory income tax to effective income tax Income Tax Expense (Benefit), Effective Income Tax Rate Reconciliation, Amount [Abstract] Summary of restricted stock unit activity Nonvested Restricted Stock Shares Activity [Table Text Block] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards Total gross carrying amount Property, Plant and Equipment, Gross Options exercised (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Weighted-Average Exercise Price (Per Share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Research and development Research and Development Expense [Member] MorphoSys/Incyte MorphoSys/Incyte [Member] MorphoSys/Incyte Consolidation and Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Net unrealized (loss) gain on marketable debt securities available-for-sale OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Diluted (in shares) Weighted-average common shares outstanding, diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Royalties owed to OMERS Royalty Liability, Owed Royalty Liability, Owed MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Numerator: Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Accounts Payable Accounts Payable [Member] Total stockholders’ equity attributable to Xencor, Inc. Equity, Attributable to Parent Gross deferred income tax assets Deferred Tax Assets, Gross Collaboration and Licensing Agreements Collaborative Arrangement Disclosure [Text Block] Mature in one year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Patents, pending issuance Patents, pending issuance Represents information pertaining to patents, pending issuance. Amortized Cost Cash and Cash Equivalents and Marketable Securities Amortized Cost This item represents the total cost of cash and cash equivalents and marketable securities. Concentration Risk Type [Domain] Concentration Risk Type [Domain] Letter of credit outstanding Letters of Credit Outstanding, Amount Total number of shares of common stock available for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Sale of Stock [Domain] Sale of Stock [Domain] Document Fiscal Period Focus Document Fiscal Period Focus All Executive Categories All Executive Categories [Member] 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Two Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Weighted-average remaining contractual life Weighted-average remaining contractual term, balance outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Assets Assets [Abstract] Expected dividend yield Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate Document Type Document Type Vir Vir Information pertaining to VIR Biotechnology (VirBio). Licensing costs Deferred Tax Liabilities License Costs Amount of deferred tax liability attributable to taxable temporary differences from licensing costs. Purchase of marketable securities Payments to Acquire Marketable Securities Weighted-average remaining contractual term, exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost Future amortization expense for patents, licenses, and other intangible assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Maximum Maximum [Member] Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Total Finite-Lived Intangible Assets, Net Furniture and fixtures Furniture and Fixtures [Member] Accounts payable Accounts Payable, Current Schedule of equity securities without readily determinable fair value Equity Securities without Readily Determinable Fair Value [Table Text Block] Schedule of weighted average assumptions used for estimation of fair value of stock options Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Total lease costs Lease, Cost Statistical Measurement [Axis] Statistical Measurement [Axis] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Loss before income tax Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Non-cash revenue recognized Collaboration Agreement, Non-Cash Revenue Recognized Collaboration Agreement, Non-Cash Revenue Recognized Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Number of expired leases Lessee, Expired Operating Lease, Number of Leases Lessee, Expired Operating Lease, Number of Leases Depreciation Deferred Tax Liabilities, Property, Plant and Equipment Name Outstanding Recovery, Individual Name Variable lease cost Variable Lease, Cost Number of additional antibody compounds Collaborative Arrangement Number Of Compounds Represents the number of compounds. Award Timing Predetermined Award Timing Predetermined [Flag] Restricted cash Restricted Cash, Noncurrent Forecast Forecast [Member] Diluted (in dollars per share) Net income (loss) per common share, diluted (in dollars per share) Earnings Per Share, Diluted Counterparty Name [Domain] Counterparty Name [Domain] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] State and Local Jurisdiction State and Local Jurisdiction [Member] Deferred revenue Increase (Decrease) in Contract with Customer, Liability Current Current Income Tax Expense (Benefit) Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Defined contribution plan employer matching contribution percent Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Preferred Stock, shares issued (in shares) Preferred Stock, Shares Issued Customer [Axis] Customer [Axis] Accounts receivable Increase (Decrease) in Accounts and Other Receivables and Contract with Customer Assets Increase (Decrease) in Accounts Receivable and Contract with Customer Assets Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Net loss Net loss Consolidated net loss Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Proceeds from sale of property and equipment Proceeds from Sale of Property, Plant, and Equipment Income tax expense Income tax expense (benefit) Income tax provision Income Tax Expense (Benefit) Other income (expense) Nonoperating Income (Expense) [Abstract] Cost not yet recognized, period of recognition Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Collaborations, licenses, milestones, and royalties Revenue recorded Revenue from Contract with Customer, Excluding Assessed Tax Purchase of intangible assets Payments to Acquire Intangible Assets Statement of Comprehensive Income [Abstract] Lease liability Deferred Tax Assets, Capitalized Lease Assets Amount before allocation of valuation allowances of deferred tax asset attributable to capitalized lease assets. Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Income Tax Jurisdiction [Axis] Income Tax Jurisdiction [Axis] All Adjustments to Compensation All Adjustments to Compensation [Member] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Additional paid-in capital Additional Paid in Capital Collaborative Arrangement and Arrangement Other than Collaborative [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Table] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Scenario [Domain] Scenario [Domain] Issuance of restricted stock units Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Restricted cash Restricted Cash Weighted average assumptions for estimated fair value of employee stock options Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions and Methodology [Abstract] Entity Address, State or Province Entity Address, State or Province Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Financial Instruments [Domain] Financial Instruments [Domain] Beginning balance (in dollars per share) Ending balance (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Liabilities and stockholders’ equity Liabilities and Equity [Abstract] Number of six month purchase periods Sharebased Compensation Arrangement by Sharebased Payment Award Number of Purchase Periods Represents the number of six month purchase periods included in the initial term of the plan. Restatement Determination Date Restatement Determination Date Options vested and expected to vest (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Alexion Alexion Pharmaceuticals, Inc. Represents information pertaining to Alexion Pharmaceuticals, Inc., with which the entity has entered into a option and license agreement. Unrealized gain on securities Deferred Tax Liabilities, Other Comprehensive Income Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Impairment charge Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount Phases of lease term Phases of Lease Term Represents the number of phases associated with a lease term. Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] 1% of participating employee contributions 1% of participating employee contributions Represents the first range at which employees' contributions are matched by a employer. Balance at the beginning of the period (in dollars per share) Balance at the end of the period (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Concentration Risk [Table] Concentration Risk [Table] Right of use asset Operating Lease, Right-of-Use Asset Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Balance at the beginning of the period (in shares) Balance at the end of the period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Zenas Common Stock Zenas Zenas Bio Pharma Limited [Member] Represents information pertaining to Zenas bio pharma. Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Deferred Revenue Deferred Revenue [Policy Text Block] Disclosure of accounting policy for deferred revenue. Genentech Genentech Represent information pertaining to Genetech. Sales-based Sales-based [Member] Represents information pertaining to sales-based potential milestones. Issuance of common stock under the Employee Stock Purchase Plan Stock Issued During Period, Value, Employee Stock Purchase Plan Schedule of weighted average assumptions used for estimation of fair value of ESPP Schedule of Share-Based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block] Granted (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Sales of Future Royalties [Line Items] Sales of Future Royalties [Line Items] Sales of Future Royalties [Line Items] Income Taxes Income Tax, Policy [Policy Text Block] Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Improvement allowance Leasehold Improvements, Gross Unrecognized Tax Benefits [Roll Forward] Unrecognized Tax Benefits [Roll Forward] PEO PEO [Member] Share development percentage Collaborative Agreement Share Percentage Of Development Cost, By Counterparty Represents the percentage of share assumed by the counter-party for development costs. Potential Milestones Type [Domain] Potential Milestones Type [Domain] Potential Milestones Type [Domain] Name Trading Arrangement, Individual Name Common stock fair value per share maximum (in dollars per share) Share Based Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Common Stock Fair Value Per Share Maximum The estimated fair value of the entity's common stock at the date of grant of stock options, used as an input in calculating the grant date fair value of the options maximum. Astria Astria [Member] Astria Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Entity Public Float Entity Public Float Number of different target programs Collaborative Arrangement Number of Target Programs Represents the number of different target programs under the collaborative agreement. Purchase period Sharebased Compensation Arrangement by Sharebased Payment Award Purchase Period Represents the purchase period during which the employee withholding amounts may be used to purchase shares. Revenue recognized of future sales Royalty Liability, Revenue Recognized of Future Sale Royalty Liability, Revenue Recognized of Future Sale Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] 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] Beginning balance (in shares) Ending balance (in shares) Shares, Outstanding Interest rate Royalty Liability, Interest Rate Royalty Liability, Interest Rate Research license term Collaborative Arrangement Research License Term Represents the research license term under the collaborative agreement. Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Beginning balance of debt related to sale of future royalties Ending balance of debt related to sale of future royalties Royalty Liability, Noncurrent Royalty Liability, Noncurrent Local Phone Number Local Phone Number Total gross carrying amount Intangible Assets, Gross (Excluding Goodwill) Valuation allowance Deferred Tax Assets, Valuation Allowance Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Total operating expenses Operating Expenses Aggregate Intrinsic Value (in thousands) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] PEO Total Compensation Amount PEO Total Compensation Amount Purchase price as percentage of stock price at the purchase date Share-Based Compensation Arrangement by Share-Based Payment Award, Purchase Price of Common Stock, Percent Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Statement of Income Location, Balance [Axis] Statement of Income Location, Balance [Axis] Options vested and expected to vest (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Common Stock Common Stock [Member] Astria Common Stock Astria/Catabasis Represents the information pertaining to Catabasis Pharmaceuticals, Inc. Interest receivable from marketable debt securities Increase (Decrease) in Accrued Investment Income Receivable Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Segment Reporting [Abstract] Segment Reporting [Abstract] Patents, Licenses, and Other Intangible Assets Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Entity Central Index Key Entity Central Index Key Scenario [Axis] Scenario [Axis] General and administrative General and Administrative Expense [Member] The 2023 Plan The 2023 Plan [Member] The 2023 Plan Unrecognized tax benefits, income tax penalties and interest accrued Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Number of collaboration and license agreements Number Of Collaboration And License Agreement Number of collaboration and license agreement. Sale of Additional Common Stock Equity [Text Block] Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Financial Instrument [Axis] Financial Instrument [Axis] Segment Reporting Segment Reporting Disclosure [Text Block] Cost sharing receivable (payable) Collaborative Arrangement Receivable Payable Related To Cost Sharing Development Activities Amount of receivable (payable) within a collaborative agreement that is associated with cost-sharing development activities. Rent expense per square foot Rent Expense Per Square Foot Amount of rent expense per square foot. Second term of plan Share Based Compensation Arrangement By Share Based Payment Award Subsequent Term Of Plan The subsequent two year period of the ESPP upon the ending of the initial two year term. Accrued interest Interest Receivable, Current Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition 5% of participating employee contributions 5% of participating employee contributions [Member] 5% of participating employee contributions Title Trading Arrangement, Individual Title Defined Contribution Plan [Table] Defined Contribution Plan [Table] Rent increase (as a percentage) Rent Expense Annual Percentage Increase Annual percentage of rent increase. Unrecognized tax benefits Balance at January 1 Balance at December 31 Unrecognized Tax Benefits Comprehensive loss attributable non-controlling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Variable Interest Entity Consolidation, Variable Interest Entity, Policy [Policy Text Block] City Area Code City Area Code Current liabilities Liabilities, Current [Abstract] Auditor Location Auditor Location Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Loss on disposal of assets Gain (Loss) on Disposition of Assets Preferred Stock Preferred Stock [Member] Defined Contribution Plan Employee Contribution [Domain] Defined Contribution Plan Employee Contribution [Domain] n/a Liability Related to the Sale of Future Royalties and Non-Cash Interest Expense on the Liability Related to the Sale of Future Royalties Future Royalties, Policy [Policy Text Block] Future Royalties, Policy Debt, net of current portion Long-Term Debt, Excluding Current Maturities Accounts Receivable Receivable [Policy Text Block] Weighted- Average Grant Date Fair Value (Per Unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Net loss per common share attributable to Xencor, Inc.: Earnings Per Share [Abstract] Equity [Abstract] Equity [Abstract] Estimated Fair Value Debt Securities, Available-for-Sale, Fair Value, Fiscal Year Maturity [Abstract] Accumulated deficit Retained Earnings (Accumulated Deficit) Potential milestone payment Revenue recognition milestone method peding Revenue Recognition Milestone Method Pending Represents the amount of consideration that will be recognized upon full completion of milestones set forth in a collaborative agreement between two parties. Equity securities impairment Deferred Tax Assets, Equity Securities Impairment Deferred Tax Assets, Equity Securities Impairment Marketable debt securities - long term Debt Securities, Noncurrent Class of Stock [Domain] Class of Stock [Domain] General and administrative General and Administrative Expense Unrealized (losses) gain recognized on equity securities Unrealized (loss) gain recorded on equity securities held at the reporting date Equity Securities, FV-NI, Unrealized Gain (Loss) Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Equity Awards Adjustments Equity Awards Adjustments [Member] Present value of lease payments Total lease liabilities Operating Lease, Liability Underlying Securities Award Underlying Securities Amount Marketable Debt and Equity Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Two Suppliers Two Suppliers [Member] Two Suppliers Amendment Flag Amendment Flag Initial cost-sharing percentage Initial Cost-sharing Percentage The initial cost-sharing percentage. Net unrealized (loss) gain on marketable debt securities available-for-sale Marketable Security, Unrealized Gain (Loss) Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Proceeds from sale of equity securities Proceeds from Sale of Equity Securities, FV-NI Sale of Stock, Number of Shares Issued in Transaction Sale of Stock, Number of Shares Issued in Transaction Mature in one year or less Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Schedule of indefinite-lived intangible assets Schedule of Indefinite-Lived Intangible Assets [Table Text Block] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Cash and cash equivalents Money Market Funds in Cash and Cash Equivalents Cash and Cash Equivalents, at Carrying Value 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] Auditor Name Auditor Name Forfeited (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Viridian Common Stock Viridian [Member] Viridian 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] Development-based Development-based [Member] Represents information pertaining to development-based potential milestones. Additional Program Additional Program [Member] Additional Program Estimated useful lives of the assets Property, Plant and Equipment, Useful Life Number of Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] ESPP Employee Stock [Member] Depreciation expense Depreciation, Depletion and Amortization, Nonproduction Accounts payable Increase (Decrease) in Accounts Payable Proceeds from issuance of common stock from Employee Stock Purchase Plan Proceeds from Stock Plans Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Deferred revenue Deferred Tax Assets, Deferred Income Pasadena, CA - office and laboratory space Pasadena, CA - office and laboratory space [Member] Represents information pertaining to the laboratory and office space in Pasadena, California. Capitalized legal costs Deferred Tax Liabilities Capitalized Legal Costs Amount of deferred tax liability attributable to taxable temporary differences from capitalized legal costs. Net loss attributable to Xencor, Inc. Net Income (Loss) Available to Common Stockholders, Basic Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] 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] Weighted average common shares used to compute net loss per share attributable to Xencor, Inc. Weighted Average Number of Shares Outstanding, Diluted [Abstract] Total assets Assets Share-based payment arrangement, plan modification, incremental cost Share-Based Payment Arrangement, Plan Modification, Incremental Cost Collection period Accounts Receivable Collection Period Represents the duration of time typical for accounts receivable collection. Accounts Receivable Collection Period [Line Items] Accounts Receivable Collection Period [Line Items] Accounts Receivable Collection Period Purchase of property and equipment Payments to Acquire Property, Plant, and Equipment Number of candidates for which option to advance for development and commercialization Collaborative Agreement, Option To Advance Number Of Candidates For Development And Commercialization Represents the number of candidates for which option to advance for development and commercialization. Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Commitments and contingencies (see note 9) Commitments and Contingencies MorphoSys MorphoSys [Member] Represents information pertaining to MorphoSys. Stock-Based Compensation Share-Based Payment Arrangement [Policy Text Block] Reconciliation of the federal statutory income tax rate to our effective income tax rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Termination Date Trading Arrangement Termination Date INmune Common Stock INmune Represents information pertaining to the counterparty, INmune Bio, Inc. (INmune). Fair Value of Financial Instruments Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] 2026 Lessee, Operating Lease, Liability, to be Paid, Year Two Marketable Securities [Abstract] Marketable Securities [Abstract] Novartis Novartis [Member] Represents information pertaining to Novartis. Mature within two years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Leasehold and tenant improvements Leaseholds and Leasehold Improvements [Member] Marketable debt securities Marketable securities Primary financial statement caption encompassing marketable securities. Net loss attributable to Xencor, Inc. Net Income (Loss) Net Income (Loss) Attributable to Parent Trading Arrangement: Trading Arrangement [Axis] Annual vesting percentage Defined Contribution Plan Annual Vesting Percentage Over Vesting Term The annual vesting percentage of a defined contribution plan over the plan's vesting period. Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Entity File Number Entity File Number Gain on sale of available-for-sale marketable debt securities Marketable Security, Realized Gain (Loss) Non-Controlling Interest Noncontrolling Interest [Member] Income Statement [Abstract] Income Statement [Abstract] Entity Address, Address Line One Entity Address, Address Line One Mabgeek Shanghai Mabgeek Biotech Co., Ltd. [Member] Shanghai Mabgeek Biotech Co., Ltd. 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Contract asset Contract with Customer, Asset, after Allowance for Credit Loss Investment Company, Change in Net Assets [Line Items] Investment Company, Change in Net Assets [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Schedule of marketable securities Marketable Securities [Table Text Block] Warrants Warrants and Rights Outstanding Adjustment to Compensation: Adjustment to Compensation [Axis] Accounts Receivable Accounts Receivable [Member] Net loss attributable to non-controlling interest Net Income (Loss) Attributable to Noncontrolling Interest Statement [Table] Subsidiary or Equity Method Investee, Sale of Stock, Type [Table] Discount on proceeds from sale Collaborative Arrangement Discount On Proceeds Received From Sale Represents the amount of discount on the proceeds from a sale associated with a collaboration agreement. Mature within two years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Conversion of convertible note Payments (Conversion) of Notes Receivable Payments (Conversion) of Notes Receivable Accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Net of Tax Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Basic (in shares) Weighted-average common shares outstanding, basic (in shares) Weighted Average Number of Shares Outstanding, Basic Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Unrealized losses, 12 months or greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Equity received in connection with license agreement Noncash Consideration Received From Revenue Contracts Amount of equity received in connection with license contract agreements. 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Equity Securities Debt and Equity Securities, FV-NI [Line Items] Statistical Measurement [Domain] Statistical Measurement [Domain] Gross Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Summary of lease costs and cash disclosures Lease, Cost [Table Text Block] Vega Vega Therapeutics, Inc. [Member] Vega Therapeutics, Inc. Unrecognized tax benefits that would impact effective tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate State Deferred Federal, State and Local, Tax Expense (Benefit) All Trading Arrangements All Trading Arrangements [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Schedule of basic and diluted net income (loss) per common share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Tax credit carryforwards Tax Credit Carryforward, Amount Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Taxes Income Taxes Paid, Net Pay vs Performance Disclosure [Line Items] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Other Performance Measure, Amount Other Performance Measure, Amount Change in state rate Effective Income Tax Rate Reconciliation, Change in State Rate, Amount Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the state rate. 2027 Finite-Lived Intangible Asset, Expected Amortization, Year Three Leases Lessee, Operating Leases [Text Block] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Operating lease cost Operating Lease, Cost Lease liabilities, net of current portion Lease liabilities - long-term Operating Lease, Liability, Noncurrent Schedule of stock options outstanding Schedule of Stock Options Outstanding [Table Text Block] Tabular disclosure of summary information pertaining to stock options outstanding. Deferred revenue Contract with Customer, Liability, Current Collaboration and License Agreement Collaboration and License Agreement [Member] Represents information pertaining to the Collaboration and License agreement. Entity Tax Identification Number Entity Tax Identification Number Increase related to prior period tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Money Market Funds in Cash and Cash Equivalents Money Market Funds [Member] Patents Patents [Member] Sale of Stock, Consideration Received on Transaction Sale of Stock, Consideration Received on Transaction Proceeds from milestone payments Proceeds from Milestone Payment Received The amount of cash inflow from milestone payments received. Plan Name [Axis] Plan Name [Axis] Collaboration and Licensing Programs [Domain] Collaboration and Licensing Programs [Domain] Information pertaining to collaboration and licensing programs within the various agreements Equity Components [Axis] Equity Components [Axis] Research and Development Expenses Research and Development Expense, Policy [Policy Text Block] Marketable debt securities Estimated Fair Value Debt Securities, Available-for-Sale Aggregate intrinsic value, balance outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Proceeds from maturities of marketable debt securities available-for-sale Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale Janssen Janssen Biotech, Inc Represents information pertaining to Janssen Biotech, Inc. Net deferred income tax asset Deferred Tax Assets, Net Major Customers Major Customers Represents information pertaining to major customers. 2029 Lessee, Operating Lease, Liability, to be Paid, Year Five Increase (decrease) in deferred tax asset valuation allowance Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Extended Vesting Periods Extended Vesting Periods [Member] Extended Vesting Periods 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] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Schedule of Available-for-sale Securities Debt Securities, Available-for-Sale [Line Items] Issuance of common stock under the Employee Stock Purchase Plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Proceeds from sale of future royalties Proceeds from Royalties Received Cash, cash equivalents, and restricted cash, beginning of year Cash, cash equivalents, and restricted cash, end of year Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Noncash interest expense Noncash Interest Expense Noncash Interest Expense Janssen Janssen [Member] Represents information pertaining to Janseen (Accretion of discount) amortization of premium on marketable debt securities Accretion (Amortization) of Discounts and Premiums, Investments Marketable equity securities Equity securities with readily determinable fair value Equity Securities, FV-NI, Current Unamortized compensation expense related to unvested stock options and ESPP Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Current assets Assets, Current [Abstract] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-Lived Intangible Assets, Major Class Name [Domain] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Stock-Based Compensation Share-Based Payment Arrangement, Noncash Expense [Abstract] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Product and Service [Domain] Product and Service [Domain] Vested (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Computers, software and equipment Computers, software and equipment Represents information pertaining to the computers, software and equipment. Cash paid for: Supplemental Cash Flow Information Cash Paid [Abstract] Supplemental Cash Flow Information Cash Paid [Abstract] Security Exchange Name Security Exchange Name Maximum annual receivable for specific sales Royalty Liability, Maximum Annual Receivable for Specific Sales Royalty Liability, Maximum Annual Receivable for Specific Sales Options exercised (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Number of additional antibodies Collaborative Arrangement Number Of Additional antibodies The number of additional antibodies in a collaboration agreement. Number of Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] State Current State and Local Tax Expense (Benefit) Licenses and other amortizable intangible assets Licenses and other amortizable intangible assets Represents information pertaining to licenses and other intangible assets. Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Research and development Research and Development Expense Second Collaboration And License Agreement Second Collaboration And License Agreement [Member] Represents information relating to second collaboration and license agreement. Common stock, shares issued (in shares) Common Stock, Shares, Issued Cost-Sharing Development Cost-Sharing Development [Member] Cost-Sharing Development Sales of Future Royalties Future Royalties Sale Disclosure [Text Block] Future Royalties Sale Disclosure Letter of credit amount Line of Credit Facility, Maximum Borrowing Capacity Concentration risk percentage Concentration Risk, Percentage Regulatory-based Regulatory-based [Member] Represents information pertaining to regulatory-based potential milestones. Proceeds from upfront payment Proceeds from Upfront Payment Proceeds from Upfront Payment Impairment loss or recoveries Marketable Securities Impairment Losses And Recoveries Amount of impairment loss or recovery related to marketable securities. Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Less accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment FC Licenses FC Licenses Information pertaining to FC Licenses member. Percentage of compensation that employees may withhold to purchase stock at a discount Share Based Compensation Arrangement by Share Based Payment Award Percentage of Compensation withheld to Purchase Shares at Discount The percentage of annual compensation that employees may elect to have withheld to purchase stock at a discount. Common stock, shares authorized (in shares) Common Stock, Shares Authorized Collaboration and Licensing Programs [Axis] Collaboration and Licensing Programs [Axis] Information pertaining to collaboration and licensing programs within the various agreements Astellas Astellas [Member] Represent information pertaining to Astellas. Entity Voluntary Filers Entity Voluntary Filers Renewal term Lessee, Operating Lease, Renewal Term Interest expense Interest Expense, Nonoperating Deferred Deferred Income Tax Expense (Benefit) Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Third Party Licensee Third Party License Agreement [Member] Third Party License Agreement Debt Debt, Current Fair Value, Recurring Fair Value, Recurring [Member] Accounts receivable Accounts Receivable, after Allowance for Credit Loss, Current Options granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Fair value, 12 months or greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Schedule of Accounts Receivable Collection Period [Table] Schedule of Accounts Receivable Collection Period [Table] Schedule of Accounts Receivable Collection Period Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Royalties paid to OMERS Royalty Liability, Payments Royalty Liability, Payments Percentage of company matching to defined contribution plan Defined Contribution Plan, Employer Matching Contribution, Percent of Match Uncertain tax position Effective Income Tax Rate Reconciliation, Uncertain Tax Position Effective Income Tax Rate Reconciliation, Uncertain Tax Position Total debt Royalty Liability, Debt, Long-Term and Short-Term, Combined Amount Royalty Liability, Debt, Long-Term and Short-Term, Combined Amount Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Document Annual Report Document Annual Report Research collaboration Research collaboration Right to collaboration or assist on a project or agreement. Vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Nonamortizable intangible assets (trademarks) Indefinite-Lived Intangible Assets (Excluding Goodwill) Amortization expense for patents, licenses, and other intangible assets Amortization of Intangible Assets Deferred revenue Contract with Customer, Liability Research and development credit Income Tax Reconciliation Research And Development Credit Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to research and development credit. Accounting Policies [Abstract] Accounting Policies [Abstract] Revenue Revenues [Abstract] Current Fiscal Year End Date Current Fiscal Year End Date Less: Imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount PEO Name PEO Name Potential Milestones Type [Axis] Potential Milestones Type [Axis] Represents information by type of potential milestones. Awards issued under the plan (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period Award Type [Domain] Award Type [Domain] Licensing Agreements Licensing Agreements [Member] Issuance of common stock upon exercise of stock awards (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Supplier Concentration Risk Supplier Concentration Risk [Member] Non-PEO NEO Non-PEO NEO [Member] Estimated economic life Finite-Lived Intangible Asset, Useful Life Additional Paid in-Capital Additional Paid-in Capital [Member] 401(k) Plan Retirement Benefits [Text Block] Other Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Recent Adopted Accounting Pronouncements and Pronouncements Not yet Effective New Accounting Pronouncements, Policy [Policy Text Block] Class of Stock [Axis] Class of Stock [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Non-cash royalties Non-Cash Royalties [Member] Non-Cash Royalties Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Name Measure Name Entity Interactive Data Current Entity Interactive Data Current Number of drug candidates Collaborative Agreement, Bispecific Drug Development, Number Of Candidates Represents the number of candidates for which bispecific drug developed. Proceeds from sale of marketable debt securities available-for-sale Proceeds from Sale of Debt Securities, Available-for-Sale Number of operating segments Number of Operating Segments Deferred income tax assets Components of Deferred Tax Assets [Abstract] Collaboration and License Agreements Collaboration and License Agreements [Member] Collaboration and License Agreements Stock-based compensation Total employee, director and non-employee stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Net deferred income tax assets Deferred Tax Assets, Net of Valuation Allowance Percentage of funding for development costs Percentage of Funding for Development Costs Percentage of funding for development costs. Supplemental disclosures of cash flow information Supplemental Cash Flow Information [Abstract] Patent costs Deferred Tax Liabilities, Deferred Expense, Capitalized Patent Costs Total other income (expense), net Nonoperating Income (Expense) Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Auditor Firm ID Auditor Firm ID Loss from operations Operating Income (Loss) Net change in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Total liabilities and stockholders’ equity Liabilities and Equity Potential Milestones Potential Milestones Type [Member] Represents information by name of potential milestones. Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Schedule of assets recorded at fair value Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Amgen Amgen Inc. [Member] Amgen Inc. Summary of Significant Accounting Policies Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Addition of right-of-use asset Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Underlying Security Market Price Change Underlying Security Market Price Change, Percent Individual: Individual [Axis] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Options forfeited (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Expected term (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term Product and Service [Axis] Product and Service [Axis] Property and Equipment Property and Equipment Property, Plant and Equipment [Line Items] Statement [Line Items] Statement [Line Items] Operating expenses Operating Expenses [Abstract] Income Tax [Table] Income Tax [Table] Disclosures pertaining to income taxes. Schedule of property and equipment Property, Plant and Equipment [Table Text Block] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Less: Tenant allowance Lessee, Operating Lease, Liability, Tenant Allowance Amount of monetary allowance granted by the landlord to a tenant for operating lease. Minimum Minimum [Member] Royalties Royalty [Member] Adoption Date Trading Arrangement Adoption Date Income taxes Increase (Decrease) in Income Taxes Receivable Collaboration and Licensing Agreements Collaboration and Licensing Agreements Collaboration and Licensing Agreements 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] Exercise Price Award Exercise Price Noncash royalty revenue related to sale of future royalties Noncash Royalty Revenue Noncash Royalty Revenue Schedule of tax effect of temporary differences that give rise to a significant portion of the deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Non-cash interest expense recognized Royalty Liability, Interest Expense Including Amortization Of Closing Costs Royalty Liability, Interest Expense Including Amortization Of Closing Costs Revenue not recognized Collaboration Agreement, Service Agreement Charges Collaboration Agreement, Service Agreement Charges Arrangement Duration Trading Arrangement Duration Cumulative net operating loss carryforwards Operating Loss Carryforwards Technology License Agreement Technology License Agreement Information relating to a Technology License Agreement. Extended Expiration Dates Extended Expiration Dates [Member] Extended Expiration Dates Stockholders’ equity Equity, Attributable to Parent [Abstract] Fair value, less than 12 months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Domestic Tax Jurisdiction Domestic Tax Jurisdiction [Member] Total investments Investments XmAb306 XmAb306 Represents information pertaining to product XmAb306. Annual increase in shares of common stock available for issuance (in shares) Share Based Compensation Arrangement by Share Based Payment Award Annual Increase in Shares Authorized Represents the annual increase in maximum number of shares (or other type of equity) approved (usually by shareholders and board of directors), for awards under the equity-based compensation plan. Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] 2028 Finite-Lived Intangible Asset, Expected Amortization, Year Four All Individuals All Individuals [Member] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Other income (expense), net Other Nonoperating Income (Expense) Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Patents, licenses, and other intangible assets, net Total intangible assets, net Intangible Assets, Net (Excluding Goodwill) Receivables [Abstract] Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Proceeds from issuance of common stock upon exercise of stock awards Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Cost not yet recognized amount Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Patents, definite life Patents, definite life Represents information pertaining to patents, definite life. Patents, licenses, and other intangible assets Finite Lived and Indefinite Lived Intangible Assets by Major Class [Line Items] Finite Lived and Indefinite Lived Intangible Assets by Major Class [Line Items] Supplier [Axis] Supplier [Axis] Risk-free interest rate, high end of range (as a percent) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Marketable debt securities Debt Securities, Current Federal Deferred Federal Income Tax Expense (Benefit) Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Stock options Stock options An arrangement whereby an employee or non-employee is entitled to receive in the future, subject to vesting and other restrictions, a number of shares in the entity at a specified price, as defined in the agreement. Common stock and pre-funded warrants issuance costs Payments of Stock Issuance Costs Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Measure: Measure [Axis] Issuance of common stock upon exercise of stock awards Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Increase related to current year tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Sale of common stock (in shares) Stock Issued During Period, Shares, New Issues Entity Emerging Growth Company Entity Emerging Growth Company Indefinite-lived Intangible Assets [Axis] Indefinite-Lived Intangible Assets [Axis] Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Expected volatility, low end of range (as a percent) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum Percent of receivable rights Contract with Customer, Percent of Receivable Rights Contract with Customer, Percent of Receivable Rights Equity Component [Domain] Equity Component [Domain] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] 2% of participating employee contributions 2% of participating employee contributions [Member] 2% of participating employee contributions Entity Shell Company Entity Shell Company Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Statement [Table] Statement [Table] Uncertain tax position payable Taxes Payable Counterparty Name [Axis] Counterparty Name [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Debt - long-term Royalty Liabilities, Long-Term Debt Royalty Liabilities, Long-Term Debt Research and License Agreement Research and License Agreement [Member] Information pertaining to a research and license agreement. Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Increase in estimated fair value of equity securities Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Cumulative Amount Maximum annual receivables Expected Royalty Interest Payments Expected Royalty Interest Payments Level 1 Fair Value, Inputs, Level 1 [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Total current assets Assets, Current Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Number of targets against which non-exclusive license is provided Collaborative Agreement, Non-exclusive license Provided, Number of FC Technologies Targets Represents the number of FC technology targets for which non-exclusive license is provided. Supplemental schedule of noncash activities Noncash Investing and Financing Items [Abstract] Milestones or royalties in transaction price Milestones Or Royalties In Transaction Price The amount of milestones or royalties in the transaction price. Accrued compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation Accrued expenses Increase (Decrease) in Accrued Liabilities Exercisable options (in shares) Exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Weighted average grant date fair value per share of options granted during the year (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Equity shares estimated fair value Equity securities without readily determinable fair value Equity Securities without Readily Determinable Fair Value, Amount Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Income Taxes Income Tax Disclosure [Text Block] 2028 Lessee, Operating Lease, Liability, to be Paid, Year Four Gilead Gilead Represents information about the company, Gilead Sciences, Inc. Lease liabilities and ROU assets Increase Decrease In Lease Liabilities and Right Of Use Assets The increase (decrease) during the reporting period relating to lease liabilities and right of use (ROU) assets. Weighted-average discount rate Operating Lease, Weighted Average Discount Rate, Percent Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Credit Facility [Axis] Credit Facility [Axis] Number of primary criteria to determine capitalization of patent Number of Primary Criteria to Determine Capitalization of Patent Represents the number of primary criteria to determine, if a patent will be capitalized initially. Entity Registrant Name Entity Registrant Name Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Depreciation and amortization Depreciation, Depletion and Amortization Initial base monthly rent Initial Monthly Base Rent The initial amount of monthly rent expense under a lease agreement. Fair Value as of Grant Date Award Grant Date Fair Value Customer Concentration Risk Customer Concentration Risk [Member] Aggregate intrinsic value, options vested and expected to vest Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Level 2 Fair Value, Inputs, Level 2 [Member] Schedule of disaggregation of revenue Disaggregation of Revenue [Table Text Block] Sale of common stock Stock Issued During Period, Value, New Issues Schedule of total employee, director and non-employee stock-based compensation expense recognized Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Restatement Determination Date: Restatement Determination Date [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Title of 12(b) Security Title of 12(b) Security Concentration Risk Type [Axis] Concentration Risk Type [Axis] Common stock, $0.01 par value: 200,000,000 authorized shares; 70,256,108 issued and outstanding shares at December 31, 2024 and 60,998,191 issued and outstanding at December 31, 2023 Common Stock, Value, Issued Document Financial Statement Error Correction [Flag] Document Financial Statement Error Correction [Flag] Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Monrovia, CA - office and laboratory space with additional space Monrovia, CA - office and laboratory space with additional space Represents information pertaining to the original lease office and laboratory space in Monrovia, CA, in addition to the additional space as included in the amended lease agreement. Payments for (proceeds from) tenant allowance Payments for (Proceeds from) Tenant Allowance Marketable equity securities - long term Equity Securities, FV-NI, Noncurrent Percentage of equity of private company Collaborative Arrangement Percentage Equity Private Company Represents the amount of interest held in a private company. Standalone selling price Collaborative Arrangement Standalone Selling Price The selling price at which the entity would sell a good or service separately to a customer. Concentrations of risk Concentration Risk [Line Items] Preferred stock, $0.01 par value: 10,000,000 authorized shares; -0- issued and outstanding shares at December 31, 2024 and 2023 Preferred Stock, Value, Issued State and local income taxes Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Gross deferred income tax liabilities Deferred Tax Liabilities, Gross Basic (in dollars per share) Net income (loss) per common share, basic (in dollars per share) Earnings Per Share, Basic Deferred tax adjustment Effective Income Tax Rate Reconciliation, Deferred Tax Adjustment Effective Income Tax Rate Reconciliation, Deferred Tax Adjustment Research service Research service Represent information pertaining to research activity. Proceeds from issuance of common stock and pre-funded warrants Proceeds from Issuance of Common Stock Cash paid for amounts included in the measurement of lease liabilities Operating Lease, Payments Cash and cash equivalents Cash and Cash Equivalents [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Nonamortizable intangible assets (trademarks) Trademarks [Member] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Purchase price as percentage of stock price at the initial offering date Share Based Compensation Arrangement by Share Based Payment Award Purchase Price of Common Stock Percentage on Initial Offering Date Represents the purchase price expressed as a percentage of the fair market value of common stock at the initial offering date. Property and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Total current liabilities Liabilities, Current Increase to tenant allowance Leasehold Improvements, Period Increase (Decrease) Leasehold Improvements, Period Increase (Decrease) Concentrations of Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] 2025 Finite-Lived Intangible Asset, Expected Amortization, Year One Restricted stock granted (in shares) Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Contribution from non-controlling interest owners Noncontrolling Interest, Increase from Subsidiary Equity Issuance Over-Allotment Option Over-Allotment Option [Member] Government Securities US Treasury and Government [Member] Equity Securities without Readily Determinable Fair Value [Table] Equity Securities without Readily Determinable Fair Value [Table] Risk-free interest rate, low end of range (as a percent) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Expected volatility, high end of range (as a percent) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum Class of warrant or right, exercise price of warrants or rights (in dollars per share) Class of Warrant or Right, Exercise Price of Warrants or Rights License Agreement License Agreement [Member] Represents information pertaining to the License Agreement. Stock-Based Compensation Share-Based Payment Arrangement [Text Block] Asset acquisition, consideration transferred Asset Acquisition, Consideration Transferred Entity Address, City or Town Entity Address, City or Town Summary of stock option activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Percentage of co-detailing activities Percentage of Co detailing Activities Percentage of co-detailing activities. Intrinsic value of options exercised Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value Stock-based compensation Share-Based Payment Arrangement, Expense Options granted (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Employer contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Schedule of finite-lived intangible assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Area of property Area of Real Estate Property Licensing costs Deferred Tax Assets, License Costs Deferred Tax Assets, License Costs 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] Right of use assets Deferred Tax Liabilities, Leasing Arrangements Abandonment of capitalized intangible assets Noncash Project Abandonment Costs Document Fiscal Year Focus Document Fiscal Year Focus Schedule of revenue by licensees Schedule of Revenue by Major Licensees [Table Text Block] Tabular disclosure of revenue by major licensees. Total Fair Value Assets, Fair Value Disclosure Sale of Future Royalty [Roll Forward] Sale of Future Royalty [Roll Forward] Sale of Future Royalty 2029 Finite-Lived Intangible Asset, Expected Amortization, Year Five Document Period End Date Document Period End Date Sale of Stock [Axis] Sale of Stock [Axis] Proceeds from non-controlling interest Proceeds from Noncontrolling Interests Impairment on equity securities Impairment on equity securities Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount Total undiscounted lease payments Lessee, Operating Lease, Liability, to be Paid Proceeds from sale of future royalties Proceeds from Future Sale of Royalties Proceeds from Future Sale of Royalties Beginning balance (in shares) Ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Insider Trading Arrangements [Line Items] 2027 Lessee, Operating Lease, Liability, to be Paid, Year Three Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Fiscal Year Maturity [Abstract] Revenue recognized Contract with Customer, Liability, Revenue Recognized Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Audit Information [Abstract] Audit Information Document Transition Report Document Transition Report Schedule of Unrecognized Tax Benefits Roll Forward Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Customer [Domain] Customer [Domain] Entity Current Reporting Status Entity Current Reporting Status Schedule of net gains and losses Gain (Loss) on Securities [Table Text Block] Accumulated Deficit Retained Earnings [Member] RSUs Restricted Stock Units (RSUs) [Member] Unrealized gain (loss) on marketable debt securities Debt Securities, Available-for-Sale, Unrealized Gain (Loss) Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Executive Category: Executive Category [Axis] Monrovia, CA - office and laboratory space Monrovia, CA - office and laboratory space [Member] Represents information pertaining to lease office and laboratory space in Monrovia, CA. Schedule of Components of Income Tax Expense (Benefit) Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Statement of Income Location, Balance [Domain] Statement of Income Location, Balance [Domain] Letter of Credit Letter of Credit [Member] Company Selected Measure Name Company Selected Measure Name