Fair Values of Assets and Liabilities - Losses Realized on Assets Measured on Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Fair Value Disclosures [Abstract]
Impaired loans	$ (503)	$ (376)
Other real estate owned	(131)	(2,909)
Total losses	$ (634)	$ (3,285)

Net losses on other real estate owned still held at the end of the period

No definition available.

Name:	fcf_FairValueMeasurementOfAssetsOnNonrecurringBasisNetLossesOnOtherRealEstateOwned
Namespace Prefix:	fcf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration