Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] GSK-HSD License Agreement GSK-HSD License Agreement [Member] GSK-HSD License Agreement Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Liability related to the sale of future royalties Beginning carrying value Ending carrying value Royalties, Liability, Noncurrent Royalties, Liability, Noncurrent Candidate costs Research And Development Expense, Candidate Costs Research And Development Expense, Candidate Costs Statistical Measurement [Domain] Statistical Measurement [Domain] Enrollment related milestone payments Enrollment Related Milestone Payments Enrollment Related Milestone Payments Short-Term Debt, Type [Axis] Short-Term Debt, Type [Axis] Title of 12(b) Security Title of 12(b) Security Subsequent Event Subsequent Event [Member] Debt Securities, Available-for-Sale [Table] Debt Securities, Available-for-Sale [Table] Document Fiscal Year Focus Document Fiscal Year Focus Operating lease, not yet commenced, number of renewal options Lessee, Operating Lease, Lease Not Yet Commenced, Number Of Renewal Options Lessee, Operating Lease, Lease Not Yet Commenced, Number Of Renewal Options Adjustment to Compensation, Amount Adjustment to Compensation Amount Credit facility, fair value Lines of Credit, Fair Value Disclosure Financial Instrument [Axis] Financial Instrument [Axis] Number of RSUs Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Segment Reporting [Abstract] Schedule of Intangible Assets Future Amortization Expense Intangible Asset, Finite-Lived, and Capitalized Cost, Software to be Sold, Leased, or Marketed, Estimated Amortization Expense [Table Text Block] Common stock, $0.001 par value: Authorized 290,000 shares; 143,796 shares issued and 141,135 outstanding as of June 30, 2026 and 138,363 shares issued and 135,702 outstanding as of September 30, 2025 Common Stock, Value, Issued 2027 Lessee, Operating Lease, Liability, to be Paid, Year One Accrued payroll and benefits Employee-related Liabilities, Current Annual installments period Cash Receivable Under Collaboration Agreement, Annual Installments Period Cash Receivable Under Collaboration Agreement, Annual Installments Period Contingent liabilities Loss Contingency Accrual Line of Credit Line of Credit [Member] Restatement Determination Date Restatement Determination Date Class of Warrant or Right [Domain] Class of Warrant or Right [Domain] Within one year Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Remainder of Fiscal Year Accrued research and development expenses Accrued Research And Development Expense, Current Accrued Research And Development Expense, Current Number of securities called by warrants (in shares) Class of Warrant or Right, Number of Securities Called by Warrants or Rights Regulatory milestone payments Regulatory Milestone Payments Regulatory Milestone Payments Conversion price (in dollars per share) Debt Instrument, Convertible, Conversion Price Amendment Flag Amendment Flag Current liabilities: Liabilities, Current [Abstract] Consolidated Entities [Axis] Consolidated Entities [Axis] Common stock repurchase price per share (in dollars per share) Shares Acquired, Average Cost Per Share Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Bisirna Therapeutics, Inc. Bisirna Therapeutics, Inc. [Member] Bisirna Therapeutics, Inc. Schedule of Investments Debt Securities, Available-for-Sale [Table Text Block] Leases [Abstract] Leases [Abstract] Other comprehensive (loss) income, net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Total long-term liabilities Liabilities, Noncurrent Consolidated Entities [Domain] Consolidated Entities [Domain] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Entity Address, State or Province Entity Address, State or Province License Licensing Agreements [Member] Granted (in shares) Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross PEO Total Compensation Amount PEO Total Compensation Amount Foreign currency translation adjustments Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Asset Acquisition Asset Acquisition [Axis] Madrigal Licensing Agreement Madrigal Licensing Agreement [Member] Madrigal Licensing Agreement Long-term liabilities: Liabilities, Noncurrent [Abstract] Share-based payment award (in shares) Restricted stock units (in shares) Beginning of period (in shares) End of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Basic (in shares) Weighted-average basic shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Contract assets included in other current assets Contract assets Contract with Customer, Asset, after Allowance for Credit Loss, Current Schedule of Awards Outstanding Share-Based Payment Arrangement, Activity [Table Text Block] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Number of reportable segments Number of Reportable Segments Total current liabilities Liabilities, Current 2030 Lessee, Operating Lease, Liability, to be Paid, Year Four Convertible Notes, Net Convertible Debt, Noncurrent Short-Term Debt, Type [Domain] Short-Term Debt, Type [Domain] Comprehensive (loss) income: Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Lease Cost Lease, Cost [Abstract] Annual fees Additional Cash Receivable Under Collaboration Agreement Additional Cash Receivable Under Collaboration Agreement Entity Address, City or Town Entity Address, City or Town Common stock shares value reserved for future issuance Common Stock Capital Shares Value Reserved For Future Issuance Common stock, capital shares value reserved for future issuance. Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Development milestone payments Development Milestone Payments Development Milestone Payments Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Shares in exchange of IPR&D assets transferred (in shares) Equity Method Investment, Shares Received Equity Method Investment, Shares Received Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Class of Stock [Axis] Class of Stock [Axis] Intangible assets, net Net Carrying Amount Intangible Asset, Finite-Lived, after Accumulated Amortization Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Less: Unamortized debt issuance costs Debt Issuance Costs, Gross Supplemental disclosure of non-cash investing activities: Cash Flow, Noncash Investing Activities Disclosure [Abstract] Cash Flow, Noncash Investing Activities Disclosure Financing Agreement Financing Agreement [Member] Financing Agreement Dividends paid Payments of Ordinary Dividends Facilities related Research And Development Expense, Facilities Related Expense Research And Development Expense, Facilities Related Expense Level 2 Fair Value, Inputs, Level 2 [Member] Accumulated Amortization Intangible Asset, Finite-Lived, Accumulated Amortization Other income (expense): Nonoperating Income (Expense) [Abstract] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Total other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Table] 2013 Plan Two Thousands Thirteen Incentive Plan [Member] Two thousands thirteen incentive plan. Thereafter Long-Term Debt, Maturity, After Year Four Long-Term Debt, Maturity, After Year Four Sales-related milestone payments Sales Related Milestone Payments Sales-related milestone payments. 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Convertible notes, net Long-Term Debt Warrant exercise price (in dollars per share) Class of Warrant or Right, Exercise Price of Warrants or Rights Percentage of commission to sales agent Percentage Of Commission On Aggregate Gross Proceeds From Sale Of Common Stock Percentage of commission on aggregate gross proceeds from sale of common stock. Schedule of Maturities of Operating Lease Liabilities on an Undiscounted Basis Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Commercial notes Commercial Notes [Member] Commercial Notes Document Period End Date Document Period End Date Changes in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Aggregate principal amount Debt Instrument, Face Amount 2028 Lessee, Operating Lease, Liability, to be Paid, Year Two Stockholders' Equity Equity [Text Block] Security Exchange Name Security Exchange Name Debt instrument term Debt Instrument, Term Treasury stock; at cost; 2,661 shares of common stock at June 30, 2026 and September 30, 2025 Treasury stock value Treasury Stock, Common, Value Granted (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price 2031 and thereafter Lessee Operating Lease, Liability, To Be Paid, Year Five And After Year Five Lessee operating lease liability payments due year five and after year five. Pre-Funded Warrants Pre-Funded Warrants [Member] Pre-Funded Warrants Convertible Notes Convertible Notes [Member] Convertible Notes Lessee Lease Description [Line Items] Lessee, Lease, Description [Line Items] Research Facility in San Diego Research Facility In San Diego [Member] Research Facility in San Diego. Development regulatory and sales milestones payments Development Regulatory And Sales Milestones Payments Development regulatory and sales milestones payments. Convertible debt Convertible Debt Accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Patrick O'Brien Trading Arrangement Plan One [Member] Patrick O'Brien Trading Arrangement Plan One Accrued research and development expenses; co-development Accrued Research And Development Co-Development Expense, Current Accrued Research And Development Co-Development Expense, Current 2013 and 2021 Incentive Plans and Other Inducement Grants Two Thousand Thirteen Equity Incentive Plan, Two Thousand Twenty One Equity Incentive Plan And Inducement Grants [Member] Two Thousand Thirteen Equity Incentive Plan, Two Thousand Twenty One Equity Incentive Plan And Inducement Grants Number of shares authorized (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Lease liabilities Current operating lease liabilities Operating Lease, Liability, Current Schedule of Property, Plant and Equipment Property, Plant, and Equipment [Table Text Block] Net (Loss) Income Per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Earnings Per Share [Abstract] Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Trading Symbol Trading Symbol Purchases of property, plant and equipment Payments to Acquire Property, Plant, and Equipment 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] Madrigal Madrigal Therapeutics Inc. [Member] Madrigal Therapeutics Inc. 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Award Timing Predetermined Award Timing Predetermined [Flag] Common Stock in Treasury Treasury Stock, Common [Member] Intangible Asset, Goodwill and Other [Abstract] Intangible Asset, Goodwill and Other [Abstract] Intrinsic value of options exercised Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value Debt Securities, Available-for-Sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Total transaction price Collaboration Arrangement, Consideration Collaboration Arrangement, Consideration Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Level 1 Fair Value, Inputs, Level 1 [Member] Inducement Plan Inducement Plan [Member] Inducement Plan Schedule of Liability Related to the Sale of Future Royalties Schedule Of Liability Related To The Sale Of Future Royalties [Table Text Block] Schedule Of Liability Related To The Sale Of Future Royalties Organization, Consolidation and Presentation of Financial Statements [Abstract] Conversion ratio Debt Instrument, Convertible, Conversion Ratio Debt Conversion Terms Two Debt Conversion Terms Two [Member] Debt Conversion Terms Two Total Lessee, Operating Lease, Liability, to be Paid Commercial milestone payments at first commercial sale Commercial Milestone Payments At First Commercial Sale Commercial milestone payments at first commercial sale. 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Total selling, general and administrative expense, excluding non-cash expense Selling, General And Administrative Expense, Excluding Noncash Expense Selling, General And Administrative Expense, Excluding Noncash Expense Operating lease renewal term Lessee, Operating Lease, Renewal Term Schedule of Computation of Basic and Diluted Net (Loss) Income Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Financing Agreement, Initial Term Loan Financing Agreement, Initial Term Loan [Member] Financing Agreement, Initial Term Loan Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Gain on VIE's sale of IPR&D assets Noncontrolling Interest, Increase From Gain On Sale Of Assets Noncontrolling Interest, Increase From Gain On Sale Of Assets Sanofi License Agreement Sanofi License Agreement [Member] Sanofi License Agreement Segment Information Segment Reporting [Text Block] Investments Investment in Debt and Equity Securities and Other Trading Assets [Text Block] Proceeds from maturities of available-for-sale securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale Long-term line of credit Long-Term Line of Credit Minimum Minimum [Member] Covenant, convertible indebtedness outstanding maximum Debt Instrument, Covenant, Convertible Indebtedness Outstanding, Maximum Debt Instrument, Covenant, Convertible Indebtedness Outstanding, Maximum Expiration Date Trading Arrangement Expiration Date Net (decrease) increase in cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Excluding Exchange Rate Effect, Including Discontinued Operation 2030 Long-Term Debt, Maturity, Year Four Schedule of Revenue Disaggregation of Revenue [Table Text Block] Class of Warrant or Right [Axis] Class of Warrant or Right [Axis] Weighted-average shares used in calculating Denominator: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Income Statement Location [Axis] Location, Statement of Income, Balance [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Total research and development expense, excluding non-cash expense Research And Development Expense, Excluding Noncash Expense Research And Development Expense, Excluding Noncash Expense Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Total noncontrolling interest and stockholders’ equity Beginning balance Ending balance Equity, Including Portion Attributable to Noncontrolling Interest Weighted- Average Remaining Contractual Term (Years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted-Average Remaining Contractual Term 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] Buildings Building [Member] Convertible debt, fair value Convertible Debt, Fair Value Disclosures Operating Segment Operating Segment [Member] Operating Segment Covenant, aggregate convertible indebtedness outstanding, maximum Debt Instrument, Covenant, Aggregate Convertible Indebtedness Outstanding, Maximum Debt Instrument, Covenant, Aggregate Convertible Indebtedness Outstanding, Maximum Number of options outstanding, exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Visirna Therapeutics, Inc. Visirna Therapeutics, Inc. [Member] Visirna Therapeutics, Inc. Common stock, shares authorized (in shares) Common Stock, Shares Authorized Milestone payment Milestone Payment Earned Milestone payment earned. Net (loss) income per share attributable to Arrowhead Pharmaceuticals, Inc.: Earnings Per Share Reconciliation [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Useful Lives Intangible Asset, Finite-Lived, Useful Life Shares of common stock issued (in shares) Sale of Stock, Number of Shares Issued in Transaction Schedule of Share Activity Related to RSUs Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Number of performance obligations Number Of Performance Obligations Number Of Performance Obligations Exercise Price Award Exercise Price CASH FLOWS FROM INVESTING ACTIVITIES: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Segment Reporting [Line Items] Segment Reporting [Line Items] MOIC payments expected to be applied to principal upon repayment Debt Instrument, Multiple Of Investment Capital Expected To Be Applied To Principal Upon Repayment Debt Instrument, Multiple Of Investment Capital Expected To Be Applied To Principal Upon Repayment Document Quarterly Report Document Quarterly Report Manufacturing equipment Manufacturing Equipment [Member] Manufacturing Equipment Underwriting Public Offering Underwriting Public Offering [Member] Underwriting Public Offering 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] Segments [Domain] Segments [Domain] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Effect of exchange rate on cash, cash equivalents and restricted cash Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation Receivables included in accounts receivable Accounts Receivable, after Allowance for Credit Loss Proceeds from sales of available-for-sale securities Proceeds from Sale of Debt Securities, Available-for-Sale Accumulated interest on the Initial Term Loan Interest Payable Less: Unamortized debt issuance costs Debt Issuance Costs, Net Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity method investments Equity Method Investments Olpasiran Agreement Olpasiran Agreement [Member] Olpasiran agreement. Future potential milestone payments payable Future Potential Milestone Payments Payable Future Potential Milestone Payments Payable Available-for-sale securities, Adjusted Basis Debt Securities, Available-for-Sale, Amortized Cost, Current Equity Component [Domain] Equity Component [Domain] Proceeds from additional tenant improvement allowance Proceeds From Tenant Improvement Allowance Proceeds From Tenant Improvement Allowance PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Secured Debt Secured Debt [Member] Credit facility, net of current portion Long-Term Line of Credit, Noncurrent Net proceeds from sale of stock Sale of Stock, Consideration Received on Transaction Adoption Date Trading Arrangement Adoption Date Proceeds from equity offering Proceeds from Issuance or Sale of Equity After one to two years Debt Securities, Available-For-Sale, Fair Value, Maturity, Allocated And Single Maturity Date, After Year One Through Two Debt Securities, Available-For-Sale, Fair Value, Maturity, Allocated And Single Maturity Date, After Year One Through Two Interest rate Debt Instrument, Interest Rate, Stated Percentage Cash dividends Dividends, Common Stock, Cash Counterparty Name [Domain] Counterparty Name [Domain] Stockholders’ equity Equity, Attributable to Parent Total other (expense) income Nonoperating Income (Expense) Equity premium Sale Of Stock, Premium On Issuance Of Shares Sale Of Stock, Premium On Issuance Of Shares Milestone payment receivable upon achievement of phase two and first patient dosed in phase three Milestone Payment Receivable Upon Achievement Of Phase Two And First Patient Dosed In Phase Three Milestone payment receivable upon achievement of phase two and first patient dosed in phase three. 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Total operating lease liabilities (includes current portion) Operating Lease, Liability Professional, outside services, and other Professional Fees Payments of issuance costs of common stock Payments of Stock Issuance Costs Insider Trading Policies and Procedures [Line Items] Number of options outstanding (in shares) Options (in shares) Beginning balance (in shares) Ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Schedule of Outstanding Balance of Credit Facility Schedule of Line of Credit Facilities [Table Text Block] Selling, general and administrative Total selling, general and administrative expense Selling, General and Administrative Expense Financing Agreement, MOIC Payment Financing Agreement, MOIC Payment [Member] Financing Agreement, MOIC Payment Private Placement Private Placement [Member] Balance Sheet Accounts Supplemental Balance Sheet Disclosures [Text Block] Patents Patents [Member] Debt Instrument, Convertible Terms Of Conversion [Domain] Debt Instrument, Convertible Terms Of Conversion [Domain] Debt Instrument, Convertible Terms Of Conversion [Domain] Change in ownership interest in consolidated VIE Noncontrolling Interest, Increase from Subsidiary Equity Issuance Development and sales milestone payments Development And Sales Milestones Payments Development And Sales Milestones Payments Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Purchase of capped calls Payments for capped call Payments for Derivative Instrument, Financing Activities Number of operating segments Number of Operating Segments Potentially dilutive securities excluded from computation of diluted earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Restricted stock units Restricted Stock Units (RSUs) [Member] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Entity Central Index Key Entity Central Index Key Less: Accumulated depreciation and amortization Property, Plant, and Equipment, Accumulated Depreciation, Depletion, and Amortization Additional paid-in capital Additional Paid in Capital, Common Stock All Adjustments to Compensation All Adjustments to Compensation [Member] Liability, Sale Of Future Royalties [Roll Forward] Liability, Sale Of Future Royalties [Roll Forward] Liability, Sale Of Future Royalties Equity [Abstract] Equity [Abstract] 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] Net cash (used in) provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation 2026 (remainder) Long-Term Debt, Maturity, Remainder of Fiscal Year Income Statement [Abstract] Income Statement [Abstract] Document Transition Report Document Transition Report Ownership [Axis] Ownership [Axis] Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Axis] Investment, Name [Axis] Investment, Name [Axis] Salaries Salary and Wage, Excluding Cost of Good and Service Sold Takeda Pharmaceutical Company Limited Takeda Pharmaceuticals United States Of America Incorporated [Member] Takeda Pharmaceuticals United States of America Incorporated. Operating expenses: Operating Expenses [Abstract] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Schedule of Finite-Lived Intangible Assets Intangible Asset, Finite-Lived [Table Text Block] Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Collaboration arrangement, written notice period Collaboration Arrangement, Termination Notice Period After Regulatory Approval Collaboration Arrangement, Termination Notice Period After Regulatory Approval City Area Code City Area Code Accumulated Other Comprehensive Income AOCI Attributable to Parent [Member] All Individuals All Individuals [Member] If-converted common stock from convertible notes Convertible Debt Securities [Member] Subsequent Events Subsequent Events [Text Block] Name Forgone Recovery, Individual Name Weighted average period to recognize pre-tax compensation expense 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Arrowhead Pharmaceuticals, Inc. [Member] Arrowhead Pharmaceuticals, Inc. 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