Document And Entity Information	6 Months Ended
	Feb. 29, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	FACTSET RESEARCH SYSTEMS INC
Document Type	10-Q
Current Fiscal Year End Date	--08-31
Entity Common Stock, Shares Outstanding	44,760,885
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	No
Document Period End Date	Feb. 29, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2