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Unearned ESOP Shares - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2013
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]    
Borrowed funds   $ 1,600,000us-gaap_DebtAndCapitalLeaseObligations
ESOP [Member]    
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]    
Compensation costs $ 733,000fcf_EsopCompensationExpense
/ us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis
= fcf_EmployeeStockOwnershipPlanMember