Document And Entity Information (USD $)	12 Months Ended
	Aug. 31, 2013	Oct. 21, 2013	Feb. 28, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	FACTSET RESEARCH SYSTEMS INC
Document Type	10-K
Current Fiscal Year End Date	--08-31
Entity Common Stock, Shares Outstanding		43,105,237
Entity Public Float			$ 3,932,642,411
Amendment Flag	false
Entity Central Index Key	0001013237
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	Aug. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY