XML 82 R69.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Derivatives - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 9 Months Ended
--- | ---
Sep. 30, 2012 Contract
Derivative Instruments [Line Items] |
Credit risk income | $ 1.3
Offset of credit risk | $ 0.2
Number of interest rate swaps | 3

X
- Definition The change in the credit risk for the period. + References No definition available. + Details
Name: | fcf_CreditRiskIncome
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | fcf_DerivativeInstrumentsLineItems
Namespace Prefix: | fcf_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Portion of the change in credit risk for the period. + References No definition available. + Details
Name: | fcf_OffsetOfCreditRisk
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of interest rate derivative instruments held by the entity at the reporting date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959 + Details
Name: | us-gaap_NumberOfInterestRateDerivativesHeld
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant