Cover - USD ($)	12 Months Ended
	Sep. 30, 2022	Oct. 28, 2022	Mar. 31, 2022
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	1-11689
Entity Registrant Name	Fair Isaac Corp
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-1499887
Entity Address, Address Line One	5 West Mendenhall, Suite 105
Entity Address, City or Town	Bozeman,
Entity Address, State or Province	MT
Entity Address, Postal Zip Code	59715
City Area Code	406
Local Phone Number	-7276
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	FICO
Security Exchange Name	NYSE
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
Entity Public Float			$ 9,599,184,596
Entity Common Stock, Shares Outstanding		24,975,618
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Central Index Key	0000814547
Current Fiscal Year End Date	--09-30
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement relating to its 2023 Annual Meeting of Stockholders (“2023 Proxy Statement”) are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. The 2023 Proxy Statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.