Document And Entity Information	3 Months Ended
	Nov. 30, 2011
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	45,113,931
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	Nov. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q1