Cash and Due from Banks - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Cash and Due from Banks [Abstract]
Cash or balances held with the Federal Reserve Bank	$ 2.9	$ 3.6

Average Reserve Balances With Federal Reserve Bank

No definition available.

Name:	fcf_AverageReserveBalancesWithFederalReserveBank
Namespace Prefix:	fcf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant