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Derivatives - Schedule of Change in Fair Value of Derivative Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative [Line Items]
Increase (decrease) in other income	$ 755	$ (6,687)	$ 141

X

- Definition

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

+ References

No definition available.

+ Details

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

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- Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration