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Income Taxes Income Taxes (Details) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2017 USD ($)
Income Tax Disclosure [Abstract] |
Restricted Stock Expense, Tax Benefit | $ 117

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- Definition Restricted Stock Expense, Tax Benefit + References No definition available. + Details
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Namespace Prefix: | fcf_
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Balance Type: | credit
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration