Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Estimated lease payments Total Lessee, Operating Lease, Liability, to be Paid Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Held to Maturity, Gross Unrealized Gains Debt Securities, Held-to-Maturity, Accumulated Unrecognized Gain Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Technology License Commitments Technology License Commitments [Member] Technology license commitments. Milestone payment receivable at start of phase two Milestone Payment Receivable At Start Of Phase Two Milestone payment receivable at start of phase two. Total gross fixed assets Property, Plant and Equipment, Gross Tax increment financing award Tax Increment Financing Award Tax Increment Financing Award Financial Instruments Financial Instruments [Domain] Statistical Measurement Statistical Measurement [Domain] Exercise of stock options (in shares) Exercised (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Weighted-average discount rate Operating Lease, Weighted Average Discount Rate, Percent Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Additional paid-in capital Additional Paid in Capital, Common Stock Sublease Agreement Sublease Agreement [Member] Sublease Agreement. NET INCOME (LOSS) Net income (loss) Net Income (Loss) Attributable to Parent Lessee Lease Description [Table] Lessee, Lease, Description [Table] Performance obligation related to agreement, upfront payment Performance Obligation Related To Agreement Upfront Payment Performance obligation related to agreement, upfront payment. Cash received as due under collaboration agreement Cash Received As Due Under Collaboration Agreement Cash received as due under collaboration agreement. Equity Component [Domain] Equity Component [Domain] Additional office space for lease Additional Land Subject To Lease Additional land subject to lease. Leases Lessee, Operating Leases [Text Block] Lessee Lease Description [Line Items] Lessee, Lease, Description [Line Items] Plan Name Plan Name [Axis] Marketable securities Debt Securities, Available-for-Sale ARO-HSD Agreement A R O H S D Agreement [Member] AROHSD agreement. Common stock shares value reserved for future issuance (in shares) Common Stock Capital Shares Value Reserved For Future Issuance Common stock, capital shares value reserved for future issuance. Unrecognized pre-tax compensation expense Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Plan Name Plan Name [Domain] 2022 (remainder of fiscal year) Lessee, Operating Lease, Liability, to be Paid, Remainder of Fiscal Year TOTAL LONG-TERM LIABILITIES Liabilities, Noncurrent Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Entity Address, State or Province Entity Address, State or Province Level 1 Fair Value, Inputs, Level 1 [Member] Weighted- Average Remaining Contractual Term Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Award Type Award Type [Axis] 2013 Incentive Plan Two Thousands Thirteen Incentive Plan [Member] Two thousands thirteen incentive plan. Planned area of the site (in sq ft) Area of Land NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities Sales-related milestone payments Sales Related Milestone Payments Sales-related milestone payments. Lease liabilities Operating Lease, Liability, Current Cancelled (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Expirations in Period Number of shares forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Other Commitments Other Commitments [Domain] Legal Entity [Axis] Legal Entity [Axis] Number of distinct performance obligations Number Of Distinct Performance Obligations Number of distinct performance obligations. 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. Weighted-average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Geographical [Axis] Geographical [Axis] CASH FLOWS FROM INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities [Abstract] Amortization/(accretion) of note premiums/discounts Investment Income, Net, Amortization of Discount and Premium Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Domain] Summary of Property and Equipment Property, Plant and Equipment [Table Text Block] Document Type Document Type Weighted- Average Exercise Price Per Share Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Office space leases (in sq ft) Land Subject to Ground Leases Number of RSUs Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Held to Maturity, Gross Unrealized Losses Debt Securities, Held-to-Maturity, Accumulated Unrecognized Loss Finite-Lived Intangible Assets, Major Class Name Finite-Lived Intangible Assets, Major Class Name [Domain] Development regulatory and sales milestones payments Development, regulatory and sales milestones payments Development Regulatory And Sales Milestones Payments Development regulatory and sales milestones payments. Research Facility in San Diego Research Facility In San Diego [Member] Research Facility in San Diego. 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 Amortization of license agreements, thereafter Finite Lived Intangible Assets Amortization Expense After Year Four Finite lived intangible assets amortization expense after year four. Asset Acquisition Asset Acquisition [Axis] Entity Shell Company Entity Shell Company Accrued expenses Increase (Decrease) in Accrued Liabilities 2023 Lessee, Operating Lease, Liability, to be Paid, Year One Cash Equivalents, Gross Unrealized Gains Cash Equivalents Gross Unrealized Gains Cash equivalents gross unrealized gains. Financial Instrument Financial Instrument [Axis] Finite-Lived Intangible Assets [Roll Forward] Finite-Lived Intangible Assets [Roll Forward] Summary of Short-term and Long-term Investments and Marketable Securities Held To Maturity Securities And Marketable Securities Table [Table Text Block] Held to maturity securities and marketable securities. Document Period End Date Document Period End Date Commercial notes (due within ninety days) Commercial Notes Due Within Ninety Days [Member] Commercial notes due within ninety days. TOTAL ASSETS Assets Marketable Securities, Fair Value Equity Securities, FV-NI, Current Shares issued to institutional investors (in shares) Shares, Issued Accrued expenses Accrued Liabilities, Current Exercised (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price NET CASH PROVIDED BY FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities Accounting Policies [Abstract] Accounting Policies [Abstract] Accrued payroll and benefits Employee-related Liabilities, Current Variable lease cost Variable Lease, Cost Other Commitments Other Commitments [Axis] Marketable Securities, Gross Unrealized Gains Equity Securities, FV- NI, Accumulated Gross Unrealized Gain Before Tax Equity Securities, FV- NI, Accumulated Gross Unrealized Gain Before Tax INCOME (LOSS) BEFORE INCOME TAXES Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Arrowhead Pharmaceuticals, Inc. stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Held to Maturity, Cost Basis Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss Cash received as due under collaboration agreement Cash Receivable As Upfront Payment Due Under Collaboration Agreement Cash receivable as upfront payment due under collaboration agreement. Assumptions Used to Value Stock Options Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Janssen Janssen Janssen Pharmaceuticals Incorporation [Member] Janssen Pharmaceuticals, Incorporation. Award Type Award Type [Domain] Weighted average period to recognize pre-tax compensation expense Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Weighted-Average Remaining Contractual Term, Exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Common stock - restricted stock units vesting Stock Issued During Period, Value, Restricted Stock Award, Gross Initial transaction price Initial Transaction Price Initial transaction price. Entity Registrant Name Entity Registrant Name Subsequent Events Subsequent Events [Text Block] Dividend yield Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate Patents Patents [Member] Entity Address, City or Town Entity Address, City or Town Commercial milestone payments at first commercial sale Commercial Milestone Payments At First Commercial Sale Commercial milestone payments at first commercial sale. Leases [Abstract] Leases [Abstract] OPERATING EXPENSES Operating Expenses [Abstract] TOTAL STOCKHOLDERS’ EQUITY Beginning balance Ending balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Minimum Minimum [Member] Marketable Securities, Gross Unrealized Losses Equity Securities, FV-NI, Accumulated Gross Unrealized Loss Before Tax Equity securities FV NI accumulated gross unrealized loss before tax. Restricted cash Restricted Cash and Cash Equivalents, Current Noncontrolling Interest Stockholders' Equity Attributable to Noncontrolling Interest Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Olpasiran and ARO-AMG1 Agreement Olpasiran And A R O A M G1 Agreement [Member] Olpasiran and ARO-AMG1 agreement. Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] 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. Trading Symbol Trading Symbol Entity File Number Entity File Number Intangible Assets Intangible Assets Disclosure [Text Block] Amortization of license agreements in 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Four Deferred revenue, net of current portion Contract with Customer, Liability, Noncurrent Total, Cost Basis Cash Equivalents Held To Maturity And Marketable Securities Amortized Cost Cash equivalents held to maturity and marketable securities amortized cost. Capital stock authorized for issuance (in shares) Capital Units, Authorized Leasehold improvements Leasehold Improvements, Gross Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Cash Equivalents, Fair Value Cash and Cash Equivalents, Fair Value Disclosure License Agreement License Agreement [Member] License agreement. Proceeds from investment in joint venture Proceeds from Contributed Capital Accounts payable Increase (Decrease) in Accounts Payable Visirna Therapeutics, Inc. Visirna Therapeutics, Inc. [Member] Visirna Therapeutics, Inc. Organization and Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Milestone payment Milestone Payment Earned Milestone payment earned. Subsequent Events [Abstract] Subsequent Events [Abstract] Volatility, maximum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Amortization expense Amortization Amortization of Intangible Assets NET INCOME (LOSS) PER SHARE - BASIC (in dollars per share) Earnings Per Share, Basic 2025 Lessee, Operating Lease, Liability, to be Paid, Year Three Construction in Progress Construction in Progress, Gross Schedule Of Held To Maturity Securities And Marketable Securities [Table] Schedule Of Held To Maturity Securities And Marketable Securities [Table] Schedule of held to maturity securities and marketable securities. Short term investments Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss, Current Counterparty Name Counterparty Name [Domain] Olpasiran Agreement Olpasiran Agreement [Member] Olpasiran agreement. TOTAL ARROWHEAD PHARMACEUTICALS INC. STOCKHOLDERS' EQUITY Stockholders' Equity Attributable to Parent CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD CASH AND CASH EQUIVALENTS AT END OF PERIOD Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Prepaid expenses Prepaid Expense, Current 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 Entity Interactive Data Current Entity Interactive Data Current Finite-lived intangible assets, accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization 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. Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Amortization of license agreements in 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Three Drug Manufacturing Facility Drug Manufacturing Facility [Member] Drug manufacturing facility. Certificate of deposits Certificate Of Deposits Certificate of deposits. Accumulated Deficit Retained Earnings [Member] Unrecognized pre-tax compensation expense Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount 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. Common Stock Common Stock [Member] Contingent consideration Business Combination, Contingent Consideration, Liability Common Stock, Share reserve for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Statement [Table] Statement [Table] 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 Operating lease renewal term Lessee, Operating Lease, Renewal Term 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. Document Quarterly Report Document Quarterly Report CURRENT ASSETS Assets, Current [Abstract] Payments for leasehold improvements, net of tenant improvement allowances Payments Of Leasehold Improvements Net Of Tenant Improvement Allowances Payments of leasehold improvements net of tenant improvement allowances. Lease liabilities, net of current portion Operating Lease, Liability, Noncurrent Grant date fair value of other than options granted Grant Date Fair Value Of Other Than Options Granted During Period Grant date fair value of the other than options granted during the period. Organization And Significant Accounting Policies [Table] Organization And Significant Accounting Policies [Table] Organization and significant accounting policies. Statistical Measurement Statistical Measurement [Axis] Asset Acquisition Asset Acquisition [Domain] Accumulated deficit Retained Earnings (Accumulated Deficit) Cash Equivalents, Cost Basis Cash Equivalents, at Carrying Value Accounts receivable Accounts Receivable, after Allowance for Credit Loss, Current Schedule Of Finite Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Equity Components [Axis] Equity Components [Axis] Fair Value, Measurements, Recurring Fair Value, Recurring [Member] Weighted-Average Exercise Price Per Share, Exercisable (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Commercial notes (due within one through three years) Commercial Note Due Within One Through Three Years [Member] Commercial Note Due Within One Through Three Years. Cancelled (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Interest income, net Interest Income (Expense), Nonoperating, Net Document Fiscal Year Focus Document Fiscal Year Focus Number of options to renew Number Of Options To Renew Number of options to renew. Takeda License Agreement Takeda Pharmaceuticals United States Of America Incorporated [Member] Takeda Pharmaceuticals United States of America Incorporated. CASH FLOWS FROM OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Statement [Line Items] Statement [Line Items] 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 TOTAL OTHER INCOME Nonoperating Income (Expense) Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Axis] California CALIFORNIA Right-of-use assets Operating Lease, Right-of-Use Asset Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Horizon Therapeutics Ireland DAC Horizon Therapeutics Ireland D A C [Member] Horizon Therapeutics Ireland DAC. Document Transition Report Document Transition Report Local Phone Number Local Phone Number Summarized Information about Stock Options Share-Based Payment Arrangement, Option, Activity [Table Text Block] OPERATING INCOME (LOSS) Operating Income (Loss) Upfront milestone payment received Upfront Milestone Payment Received Upfront milestone payment received. Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Milestone payments Milestone Payments Milestone payments. Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Interest in joint venture Noncontrolling Interest, Increase from Subsidiary Equity Issuance Provision for income taxes Income Tax Expense (Benefit) Geographical [Domain] Geographical [Domain] Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Table] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share 2026 Lessee, Operating Lease, Liability, to be Paid, Year Four Income Statement [Abstract] Income Statement [Abstract] Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Additional Paid-In Capital Additional Paid-in Capital [Member] Licensing Agreement Licensing Agreements [Member] Balance Sheet Location Balance Sheet Location [Domain] Document Fiscal Period Focus Document Fiscal Period Focus Intrinsic value of options exercised Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value Weighted average shares outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Volatility, minimum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum Less: Accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Computers, software, office equipment and furniture Computers Software Office Equipment And Furniture Gross Computers, software, office equipment and furniture gross. Expected life (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term Total, Fair Value Cash Equivalents Held To Maturity And Marketable Securities Fair Value Cash equivalents held to maturity and marketable securities fair value. Collaborative Arrangement and Arrangement Other than Collaborative Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Novartis Novartis [Member] Novartis. Common stock, $0.001 par value; 145,000 shares authorized; 105,795 and 104,327 shares issued and outstanding as of June 30, 2022 and September 30, 2021, respectively Common Stock, Value, Issued Outside Of Equity Compensation Plans Outside Of Equity Compensation Plans [Member] Outside of equity compensation plans. Decrease in cash and investments Increase (Decrease) In Cash And Investments Increase decrease in cash and investments. License and Co-Funding Agreement License And Co Funding Agreement [Member] License and co-funding agreement. 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 Common stock - restricted stock units vesting (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Cash Equivalents, Gross Unrealized Losses Cash Equivalents Gross Unrealized Losses Cash equivalents gross unrealized losses. Aggregate Intrinsic Value, Exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value Short-term lease cost Short-Term Lease, Cost Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Impairment Impairment of Intangible Assets, Finite-Lived Foreign currency translation adjustments Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Organization And Significant Accounting Policies [Line Items] Organization And Significant Accounting Policies [Line Items] Organization and significant accounting policies. At The Market Agreement At The Market Agreement [Member] At-the-market agreement. Corporate Headquarters In Pasadena Corporate Headquarters In Pasadena [Member] Corporate Headquarters in Pasadena Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Expected leasehold improvements, net of tenant improvement allowances Expected Payments Of Leasehold Improvements Net Of Tenant Improvement Allowances Expected payments of leasehold improvements, net of tenant improvement allowances. CURRENT LIABILITIES Liabilities, Current [Abstract] Proceeds from the exercises of stock options Proceeds from Stock Options Exercised Common stock, shares issued (in shares) Common Stock, Shares, Issued Deferred revenue Contract liabilities Contract with Customer, Liability, Current Certificate of deposit (due within one year) Certificate Of Deposit Due Within One Year [Member] Certificate of deposit due within one year. Number of distinct bundle Number Of Distinct Bundle Number of distinct bundle. Collaboration Agreement Collaboration Agreement [Member] Collaboration agreement. Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Amendment Flag Amendment Flag Facilities Facilities [Member] Facilities. Amortization period of intangible assets Finite-Lived Intangible Asset, Useful Life NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities Operating lease cost Operating Lease, Cost ARO-XDH A R O X D H Agreement [Member] ARO-XDH Agreement. COMPREHENSIVE INCOME (LOSS) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Entity Current Reporting Status Entity Current Reporting Status Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Other assets Other Assets, Noncurrent Number of Options Outstanding, Exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Depreciation and amortization expense for property and equipment Depreciation, Depletion and Amortization Common Stock Purchase Agreement Common Stock Purchase Agreement [Member] Common stock purchase agreement. Lease term Lessee, Operating Lease, Term of Contract Counterparty Name Counterparty Name [Axis] Number of options outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Cash and Cash Equivalents Cash and Cash Equivalents [Axis] Janssen Janssen Pharmaceuticals And Johnson And Johnson Innovation J J D C Incorporation [Member] Janssen Pharmaceuticals and Johnson And Johnson Innovation JJDC Incorporation. Total, Gross Unrealized Losses Cash Equivalents Held To Maturity And Marketable Securities Gross Unrealized Losses Cash equivalents held to maturity and marketable securities gross unrealized losses. Schedule Of Stock By Class [Table] Schedule of Stock by Class [Table] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Property and equipment, net Property and equipment, net Property, Plant and Equipment, Net Verona Technology Park Verona Technology Park [Member] Verona technology park. Operating lease cash payments Operating Lease, Payments Employee Stock Option Share-Based Payment Arrangement, Option [Member] Amgen Amgen Incorporated [Member] Amgen Incorporated. Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Other income (expense) Other Nonoperating Income (Expense) Balance Sheet Location Balance Sheet Location [Axis] Common stock, shares authorized (in shares) Common Stock, Shares Authorized License Collaboration And Stock Purchase Agreement License Collaboration And Stock Purchase Agreement [Member] License collaboration and stock purchase agreement. TOTAL OPERATING EXPENSES Operating Expenses Maximum Maximum [Member] Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Deferred revenue Increase (Decrease) in Contract with Customer, Liability TOTAL CURRENT ASSETS Assets, Current Entity Small Business Entity Small Business Other Commitments [Table] Other Commitments [Table] Beginning balance (in shares) Ending balance (in shares) Shares, Outstanding Measurement Frequency Measurement Frequency [Domain] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Deferred Revenue Deferred Revenue [Member] Deferred revenue. Intangible assets, net Intangible assets subject to amortization, beginning balance Intangible assets subject to amortization, ending balance Finite-Lived Intangible Assets, Net Number of Options Outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Property and Equipment Property, Plant and Equipment Disclosure [Text Block] 2027 and thereafter Lessee Operating Lease Liability Payments Due Year Five And After Year Five Lessee operating lease liability payments due year five and after year five. Aggregate Intrinsic Value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Accounts receivable Increase (Decrease) in Accounts Receivable Title of 12(b) Security Title of 12(b) Security Commercial Notes Commercial Notes Commercial Notes. Proceeds from sale of investments Proceeds from Sale, Maturity and Collection of Investments Consolidated Entities [Axis] Consolidated Entities [Axis] Class Of Stock [Line Items] Class of Stock [Line Items] Total operating lease liabilities (includes current portion) Operating Lease, Liability Land Land Milestone payments Milestone Payment Received Milestone payment received. 2004 Equity Incentive Plan Two Thousands Four Equity Incentive Plan [Member] Two thousands four equity incentive plan. Schedule of Intangible Assets Schedule of Intangible Assets and Goodwill [Table Text Block] Investments, Debt and Equity Securities [Abstract] Amortization of license agreements in 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Two Research equipment Research Equipment Gross Research equipment gross. ARO-XDH Supply Agreement A R O X D H Supply Agreement [Member] ARO-XDH supply agreement. LIABILITIES, NONCONTROLLING INTEREST AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] Granted (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Percentage of eligible to receive tiered royalties on net sales Percentage Of Eligible To Receive Tiered Royalties On Net Sales Percentage of eligible to receive tiered royalties on net sales. Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Land purchased, number of acres Number Of Acres Of Land Purchased Number of acres of land purchased. Accounts payable Accounts Payable, Current OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX: Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Marketable Securities, Cost Basis Equity Securities, FV-NI, Cost Halozyme, Inc. Halozyme Inc [Member] Halozyme, Inc. Entity Filer Category Entity Filer Category Proceeds from the issuance of common stock Proceeds from Issuance of Common Stock Weighted average shares outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Basic STOCKHOLDERS’ EQUITY Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Contingent liabilities Loss Contingency Accrual Stock-based compensation expense Share-Based Payment Arrangement, Expense Commitments and contingencies (Note 7) Commitments and Contingencies Security Exchange Name Security Exchange Name Beginning balance (in dollars per share) Ending balance (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price REVENUE Revenues Revenue from Contract with Customer, Excluding Assessed Tax GSK Glaxosmithkline Intellectual Property Limited [Member] Glaxosmithkline Intellectual Property Limited. Colorado Owner, LLC Colorado Owner L L C [Member] Colorado Owner, LLC. Shares reserve for issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance LONG-TERM LIABILITIES Liabilities, Noncurrent [Abstract] Cover [Abstract] Cover [Abstract] Level 3 Fair Value, Inputs, Level 3 [Member] Number of agreements Number Of Agreements Number of agreements. Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Stock-Based Compensation Share-Based Payment Arrangement [Text Block] Held to Maturity, Fair Value Short-term investments Debt Securities, Held-to-Maturity, Fair Value JNJ-3989 (ARO-HBV) Agreement J N J3989 A R O H B V Agreement [Member] JNJ-3989 (ARO-HBV) Agreement. Long term investments Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss, Noncurrent Noncontrollling Interest Noncontrolling Interest [Member] Commercial notes (due within one year) Commercial Note Due Within One Year [Member] Commercial Note Due Within One Year. TOTAL LIABILITIES, NONCONTROLLING INTEREST AND STOCKHOLDERS’ EQUITY Liabilities and Equity Collaborative Arrangement and Arrangement Other than Collaborative Collaborative Arrangement and Arrangement Other than Collaborative [Axis] State income tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Amount Organization, Consolidation and Presentation of Financial Statements [Abstract] Level 2 Fair Value, Inputs, Level 2 [Member] Purchases of investments Payments to Acquire Investments Current Fiscal Year End Date Current Fiscal Year End Date Amount intends to invest for buildout of the facilities Amount Intends To Invest For Buildout Of Facilities Amount intends to invest for buildout of facilities. Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Marketable securities Marketable Securities, Current Finite Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] NET INCOME (LOSS) PER SHARE - DILUTED (in dollars per share) Earnings Per Share, Diluted Sale of Stock Sale of Stock [Domain] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition TOTAL CURRENT LIABILITIES Liabilities, Current Risk-free interest rate, minimum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum 2024 Lessee, Operating Lease, Liability, to be Paid, Year Two Other current assets Other Assets, Current Summary of Share Activity Related to RSUs Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Collaboration and License agreements Collaboration And License Agreement [Member] Collaboration and license agreements. OTHER INCOME Nonoperating Income (Expense) [Abstract] Risk-free interest rate, maximum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Total, Gross Unrealized Gains Cash Equivalents Held To Maturity And Marketable Securities Gross Unrealized Gains Cash equivalents held to maturity and marketable securities gross unrealized gains. Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis Lessee, Operating Lease, Liability, Maturity [Table Text Block] Certificate of deposit (due within one through two years) Certificate Of Deposit Due Within One Through Two Years [Member] Certificate of deposit due within one through two years. Entity Address, Address Line Two Entity Address, Address Line Two Entity Address, Address Line One Entity Address, Address Line One JNJ-75220795 (ARO-JNJ1) J N J75220795 A R O J N J1 [Member] JNJ 75220795 ARO JNJ1. Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Unrealized (gains) losses on marketable securities Marketable Securities, Unrealized Gain (Loss) Cash and Cash Equivalents Cash and Cash Equivalents [Domain] Equity [Abstract] Equity [Abstract] Vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Entity Tax Identification Number Entity Tax Identification Number Equity securities sold Proceeds from Sale of Equity Securities, FV-NI Wisconsin WISCONSIN Number of restricted stock units outstanding (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding, Number JJDC Johnson And Johnson Innovation J J D C Incorporation [Member] Johnson and Johnson Innovation-JJDC, Incorporation. Amortization of license agreements remainder of fiscal year 2022 Finite-Lived Intangible Asset, Expected Amortization, Remainder of Fiscal Year Contract assets Contract with Customer, Asset, after Allowance for Credit Loss, Current Consolidated Entities [Domain] Consolidated Entities [Domain] Research and development Research and Development Expense (Excluding Acquired in Process Cost) Long-term investments Held To Maturity Securities Fair Value Non Current Held to maturity securities fair value non current. NET INCREASE (DECREASE) IN CASH Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Accrued Expenses Accrued Liabilities [Member] Entity Central Index Key Entity Central Index Key Estimated payments for operating expenses Estimated Payments For Operating Expenses Year One Estimated payments for operating expenses year one. Measurement Frequency Measurement Frequency [Axis] Weighted- Average Grant Date Fair Value Per Share Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Finite-Lived Intangible Assets by Major Class Finite-Lived Intangible Assets by Major Class [Axis] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Collaboration and License Agreements Collaborative Arrangement Disclosure [Text Block] Marketable securities Marketable Securities [Member] Marketable securities. Entity [Domain] Entity [Domain] City Area Code City Area Code General and administrative expenses General and Administrative Expense ASSETS Assets [Abstract] Other Commitments [Line Items] Other Commitments [Line Items] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Sale of Stock Sale of Stock [Axis] Grant date fair value of the options granted Grant Date Fair Value Of Options Granted During Period Grant date fair value of the options granted during the period. Laboratory and Office Facility Laboratory And Office Facility [Member] Laboratory and office facility. CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Weighted average grant date fair value per share of options granted Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Research Facility in Madison Research Facility In Madison [Member] Research facility in Madison. Other Increase (Decrease) in Other Operating Liabilities Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Amortization of license agreements in 2023 Finite-Lived Intangible Asset, Expected Amortization, Year One