Fair Value Measures - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
May 31, 2022	May 31, 2022
Fair Value Disclosures [Abstract]
Impairment charges	$ 48.8	$ 62.2

Impairment Of Long Lived Assets To Be Disposed Of and Operating Lease, Impairment Loss

No definition available.

Name:	fds_ImpairmentOfLongLivedAssetsToBeDisposedOfAndOperatingLeaseImpairmentLoss
Namespace Prefix:	fds_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration