Cover - shares	9 Months Ended
	Jun. 30, 2023	Jul. 21, 2023
Cover [Abstract]
Document Type	10-Q/A
Document Period End Date	Jun. 30, 2023
Document Quarterly Report	true
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, Postal Zip Code	59715
Entity Address, City or Town	Bozeman,
Entity Address, State or Province	MT
City Area Code	406
Local Phone Number	982-7276
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	FICO
Security Exchange Name	NYSE
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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		24,857,214
Entity Central Index Key	0000814547
Document Fiscal Period Focus	Q3
Amendment Flag	true
Document Fiscal Year Focus	2023
Current Fiscal Year End Date	--09-30
Amendment Description	EXPLANATORY NOTEFair Isaac Corporation (the “Company”) is filing this Amendment No. 1 on Form 10-Q/A (this “Amendment”) to its Quarterly Report on Form 10-Q for the fiscal quarter ended June 30, 2023, which was originally filed with the Securities and Exchange Commission on August 2, 2023 (“Original Filing”), solely to include inline eXtensible Business Reporting Language (“iXBRL”) data tagging that was inadvertently omitted from the disclosure included in the Original Filing under Part II, “Item 5. Other Information”. This Amendment also includes new Exhibit 31 certifications pursuant to Section 302 of the Sarbanes-Oxley Act of 2002, but since this Amendment does not contain or amend any financial statements or any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4, and 5 of such certifications have been omitted. Except for the items specifically noted above, this Amendment does not modify or update any disclosures in the Original Filing. Accordingly, this Amendment does not reflect events occurring after the filing of the Original Filing or modify or update any disclosures, other than those identified above.