XML 86 R73.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Subsequent Event (Details) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2017 USD ($) branch
Subsequent Events [Abstract] |
Business Acquisition, Total Assets | $ 550.0
Branch Acquisition, Number of Branches | branch | 9
Business Acquisition, Escrow Funded | $ 21.3

X
- Definition Branch Acquisition, Number of Branches + References No definition available. + Details
Name: | fcf_BranchAcquisitionNumberofBranches
Namespace Prefix: | fcf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Business Acquisition, Escrow Funded + References No definition available. + Details
Name: | fcf_BusinessAcquisitionEscrowFunded
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Business Acquisition, Total Assets + References No definition available. + Details
Name: | fcf_BusinessAcquisitionTotalAssets
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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