Cover Page - USD ($) $ in Billions	12 Months Ended
Cover Page - USD ($) $ in Billions	Sep. 30, 2024	Nov. 20, 2024	Mar. 31, 2024
Cover [Abstract]
Document Type	10-K/A
Document Annual Report	true
Document Period End Date	Sep. 30, 2024
Current Fiscal Year End Date	--09-30
Document Transition Report	false
Entity File Number	001-38042
Entity Registrant Name	ARROWHEAD PHARMACEUTICALS, INC.
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	46-0408024
City Area Code	626
Local Phone Number	304-3400
Entity Address, Address Line One	177 E. Colorado Blvd
Entity Address, Address Line Two	Suite 700
Entity Address, City or Town	Pasadena
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91105
Security12b Title	Common Stock, $0.001 par value
Trading Symbol	ARWR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Document Financial Statement Error Correction [Flag]	false
Entity Public Float			$ 3.0
Entity Common Stock Shares Outstanding		124,434,442
Documents Incorporated by Reference	None.
Amendment Description	Arrowhead Pharmaceuticals, Inc. (the “Company” or “Arrowhead”) is filing this Amendment No. 1 on Form 10-K/A (this “Amendment”) to its Annual Report on Form 10-K for the year ended September 30, 2024 filed with the Securities and Exchange Commission (the “SEC”) on November 26, 2024 (the “Original Report”) solely to include the information required by Items 10 through 14 of Part III of Form 10-K (the “Part III Information”) not included in the Original Report in order to comply with General Instruction G.3 of Form 10-K. The Company’s Definitive Proxy Statement on Schedule 14A containing the Part III Information was filed with the SEC on January 29, 2025 (the “Proxy Statement”) was filed three minutes after the filing deadline on the 120th day after the Company’s fiscal year end. Except as noted below, the Part III Information included in this Amendment is as of January 28, 2025.Pursuant to Rule 12b-15 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), this Amendment also contains new certifications pursuant to Section 302 of the Sarbanes-Oxley Act of 2002, which are filed herewith. Because no financial statements have been included in this Amendment, and this Amendment does not contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4, and 5 of the certifications have been omitted. Similarly, because no financial statements have been included in this Amendment, certifications pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 have been omitted.Except as described above, no other changes have been made to the Original Report and this Amendment does not modify, amend or update in any way any of the financial or other information contained in the Original Report or the Proxy Statement. This Amendment does not reflect events that may have occurred subsequent to the date of filing of the Original Report or the Proxy Statement. Accordingly, this Amendment should be read in conjunction with the Original Report and the Proxy Statement.
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Entity Central Index Key	0000879407
Amendment Flag	true

ARROWHEAD PHARMACEUTICALS, INC. 10-K/A