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Regulatory Restrictions and Capital Adequacy - Additional Information (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Cash dividends declared per common share | $ 0.18 | $ 0.12

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- Definition Cash Dividend Per Common Share Declared + References No definition available. + Details
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Namespace Prefix: | fcf_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

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