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Other Long-term Debt - Additional Information (Detail) (FHLB [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Loan advance amount	7.5
LIBOR [Member]
Floating rate Period	3 month

X

- Definition

Floating Interest Rate Period

+ References

No definition available.

+ Details

Name:	fcf_FloatingInterestRatePeriod
Namespace Prefix:	fcf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Term loan advances aggregate amount.

+ References

No definition available.

+ Details

Name:	fcf_TermLoanAdvancesAggregateAmount
Namespace Prefix:	fcf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant