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Unearned ESOP Shares - Additional Information (Detail) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |
Borrowed funds |  | $ 1,600,000 |
ESOP [Member] |  |  |
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |
Compensation costs | $ 733,000 | $ 717,000 | $ 783,000

X
- Definition Compensation expense relation to the ESOP. + References No definition available. + Details
Name: | fcf_EsopCompensationExpense
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, collateralized financings, and capital lease obligations. + References No definition available. + Details
Name: | us-gaap_BorrowedFunds
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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