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Cash and Due from Banks - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Cash And Due From Banks [Line Items]
Cash or balances held with the Federal Reserve Bank	$ 3.6	$ 26.0

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- Definition

Average Reserve Balances With Federal Reserve Bank

+ References

No definition available.

+ Details

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

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- Details

Name:	fcf_CashAndDueFromBanksLineItems
Namespace Prefix:	fcf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration