Derivatives - Schedule of Changes in Fair Value of Derivative Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Increase in other income	$ 989	$ 606

Change in the fair value of derivative assets and derivative liabilities attributable to credit risk included in other income.

No definition available.

Name:	fcf_ChangeInOtherIncomeDueToCreditRiskOnInterestRateSwaps
Namespace Prefix:	fcf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration