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Subsequent Event - Additional Information (Detail) (Subsequent Event [Member], USD $) In Millions, unless otherwise specified | 1 Months Ended |
--- | --- | ---
Jan. 31, 2013 | Jan. 29, 2013
Subsequent Event [Member] |  |
Subsequent Event [Line Items] |  |
Additional shares authorized for repurchase |  | $ 25.0
Redemption of capital securities | $ 32.5 |
Redemption rate | 9.50% |

X
- Definition Additional Amount Of Shares Authorized To Be Repurchased + References No definition available. + Details
Name: | fcf_AdditionalAmountOfSharesAuthorizedToBeRepurchased
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Outstanding amount of capital securities to be redeemed. + References No definition available. + Details
Name: | fcf_AmountOfCapitalSecuritiesToBeRedeemed
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Stock Repurchased During Period As Percentage Of Shares Outstanding + References No definition available. + Details
Name: | fcf_StockRepurchasedDuringPeriodAsPercentageOfSharesOutstanding
Namespace Prefix: | fcf_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration