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Counterparty Name [Domain] Counterparty Name [Domain] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Schedule of Shares of Common Stock and Preferred Stock Schedule of Stock by Class [Table Text Block] Cash, cash equivalents and restricted cash BEGINNING OF PERIOD END OF PERIOD Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Inducement Awards Inducement Awards [Member] Inducement Awards 2026 Lessee, Operating Lease, Liability, to be Paid, Year Two Research equipment Research Equipment [Member] Research Equipment Common stock offering price (in dollars per share) Sale of Stock, Price Per Share Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Variable lease cost Variable Lease, Cost Initial transaction price Initial Transaction Price Initial transaction price. 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Weighted average period to recognize pre-tax compensation expense Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Maximum Maximum [Member] Document Type Document Type Tabular List, Table Tabular List [Table Text Block] Short-term lease cost Short-Term Lease, Cost Entity Address, Address Line One Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Two Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Additional remaining development regulatory and sales milestones payments Additional Remaining Development Regulatory And Sales Milestones Payments Additional remaining development regulatory and sales milestones payments. 2021 Incentive Plan Two Thousand Twenty One Incentive Plan [Member] Two thousand twenty one incentive plan. Stock-Based Compensation Share-Based Payment Arrangement [Text Block] Net increase in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Weighted- Average Exercise Price Per Share Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Ken Myszkowski March 28 Plan 3 [Member] Ken Myszkowski March 28 Plan 3 GSK License Agreement GSK License Agreement [Member] GSK License Agreement Schedule of Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Other liabilities Other Liabilities, Current Income Statement [Abstract] Income Statement [Abstract] Common stock issued, net of offering costs (in shares) Stock Issued During Period, Shares, New Issues Number of shares forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Title of 12(b) Security Title of 12(b) Security Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Ken Myszkowski March 28 Plan 4 [Member] Ken Myszkowski March 28 Plan 4 Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Visirna Therapeutics, Inc. Visirna Therapeutics, Inc. [Member] Visirna Therapeutics, Inc. Milestone payment Milestone Payment Earned Milestone payment earned. 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Land Land [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Financial Instrument [Axis] Financial Instrument [Axis] Entity Interactive Data Current Entity Interactive Data Current Olpasiran Agreement Olpasiran Agreement [Member] Olpasiran agreement. Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Total Shareholder Return Amount Total Shareholder Return Amount Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Supplemental disclosure of noncash investing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Ken Myszkowski March 28 Plan 2 [Member] Ken Myszkowski March 28 Plan 2 Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Axis] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] 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. Accumulated deficit Retained Earnings (Accumulated Deficit) Measure: Measure [Axis] Drug Manufacturing Facility Drug Manufacturing Facility [Member] Drug manufacturing facility. Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Common stock - restricted stock units vesting (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Name Outstanding Recovery, Individual Name 2004 Equity Incentive Plan, 2013 Equity Incentive Plan, 2021 Equity Incentive Plan and Inducement Grants Two Thousand Four Equity Incentive Plan Two Thousand Thirteen Equity Incentive Plan Two Thousand Twenty One Equity Incentive Plan And Inducement Grants [Member] Two thousand four equity incentive plan two thousand thirteen equity incentive plan Two thousand twenty one equity incentive plan and inducement grants. Collaboration And License Agreements [Abstract] Collaboration And License Agreements [Abstract] Collaboration and license agreements. Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Current assets: Assets, Current [Abstract] Leases [Abstract] Leases [Abstract] Other Commitments [Line Items] Other Commitments [Line Items] Entity Address, State or Province Entity Address, State or Province Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Counterparty Name [Axis] Counterparty Name [Axis] CASH FLOWS FROM OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] William Waddill [Member] William Waddill 2025 Finite-Lived Intangible Asset, Expected Amortization, Year One Schedule Of Held To Maturity Securities And Marketable Securities [Line Items] Schedule Of Held To Maturity Securities And Marketable Securities [Line Items] Schedule of held to maturity securities and marketable securities. 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Development and sales milestone payments Development And Sales Milestones Payments Development And Sales Milestones Payments PEO PEO [Member] California CALIFORNIA Liability, Sale Of Future Royalties [Roll Forward] Liability, Sale Of Future Royalties [Roll Forward] Liability, Sale Of Future Royalties Beginning balance (in shares) Ending balance (in shares) Shares, Outstanding Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Sale of Stock [Axis] Sale of Stock [Axis] Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Customer [Domain] Customer [Domain] Number of options to renew Number Of Options To Renew Number of options to renew. Takeda Takeda Pharmaceuticals United States Of America Incorporated [Member] Takeda Pharmaceuticals United States of America Incorporated. Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Total operating lease liabilities (includes current portion) Operating Lease, Liability Summary of Awards Outstanding Share-Based Payment Arrangement, Activity [Table Text Block] Asset Acquisition Asset Acquisition [Axis] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Horizon Horizon Therapeutics Ireland DAC [Member] Horizon Therapeutics Ireland DAC. Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Measurement Frequency Measurement Frequency [Domain] Shares reserve for issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance All Executive Categories All Executive Categories [Member] Long-term liabilities: Liabilities, Noncurrent [Abstract] Liability Related to the Sale of Future Royalties Liability Related To The Sale Of Future Royalties [Text Block] Liability Related To The Sale Of Future Royalties Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Plan Name Plan Name [Axis] James Hamilton [Member] James Hamilton Lease Assets and Liabilities Assets and Liabilities, Lessee [Abstract] Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Earnings Per Share [Abstract] Common stock, $0.001 par value: Authorized 290,000 shares; issued and outstanding 124,133 and 107,312 shares Common Stock, Value, Issued U.S. government bonds US Government Debt Securities [Member] General and administrative General and Administrative Expense Ken Myszkowski March 28 Plan 1 [Member] Ken Myszkowski March 28 Plan 1 Cash received for amounts included in the measurement of lease liabilities: Cash Flow, Operating Activities, Lessee, Cash Received For Amounts Included In Measurement Of Lease Liabilities [Abstract] Cash Flow, Operating Activities, Lessee, Cash Received For Amounts Included In Measurement Of Lease Liabilities Organization, Consolidation and Presentation of Financial Statements [Abstract] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Total current assets Assets, Current Receivables included in accounts receivable Accounts Receivable, after Allowance for Credit Loss All Individuals All Individuals [Member] Supplementary disclosure of cash flows: Supplemental Cash Flow Information [Abstract] Cash paid for amounts included in the measurement of lease liabilities: Cash Flow, Operating Activities, Lessee [Abstract] Other, net Other Nonoperating Income (Expense) Entity Filer Category Entity Filer Category Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Statement [Table] Statement [Table] Current Fiscal Year End Date Current Fiscal Year End Date Liability Related To The Sale Of Future Royalties [Abstract] Liability Related To The Sale Of Future Royalties Novartis Novartis [Member] Novartis. 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At The Market Agreement At The Market Agreement [Member] At-the-market agreement. Furniture Furniture and Fixtures [Member] Corporate Headquarters In Pasadena Corporate Headquarters In Pasadena [Member] Corporate Headquarters in Pasadena Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Total Arrowhead Pharmaceuticals, Inc. stockholders’ equity Equity, Attributable to Parent Schedule Of Finite Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Number of distinct bundle Number Of Distinct Bundle Number of distinct bundle. Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Royalty payment threshold Royalty Payment Threshold Royalty Payment Threshold Finite-Lived Intangible Assets, Major Class Name Finite-Lived Intangible Assets, Major Class Name [Domain] Foreign currency translation adjustments Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Facilities Facilities [Member] Facilities. 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