Subsequent Event - Additional Information (Detail) (Subsequent Event [Member], USD $)	Jan. 28, 2014
Subsequent Event [Member]
Subsequent Event [Line Items]
Additional shares authorized for repurchase	$ 25,000,000.0

Additional Amount Of Shares Authorized To Be Repurchased

No definition available.

Name:	fcf_AdditionalAmountOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	fcf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant