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

X
- 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