Document And Entity Information - shares	6 Months Ended
	Feb. 28, 2018	Mar. 29, 2018
Document Information [Line Items]
Entity Registrant Name	FACTSET RESEARCH SYSTEMS INC
Entity Central Index Key	0001013237
Trading Symbol	fds
Current Fiscal Year End Date	--08-31
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding (in shares)		38,874,450
Document Type	10-Q
Document Period End Date	Feb. 28, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Amendment Flag	false