Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Gross Loans Receivable

No definition available.

Name:	fcf_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedGrossLoansReceivable
Namespace Prefix:	fcf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Business Combination, Recognized Identifiable Assets and Liabilities Assumed, Gross Loans Receivable, Credit Market Adjustment

+ References

No definition available.

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460

+ Details

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the number of stores.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfStores
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=fcf_FirstCommunityBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisition - Narrative (Details) $ in Thousands		12 Months Ended
Acquisition - Narrative (Details) $ in Thousands	Oct. 01, 2015 USD ($) branch	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition [Line Items]
Costs related to the acquisition		$ 922	$ 0	$ 0
First Community Bank
Business Acquisition [Line Items]
Total consideration paid	$ 14,750
Gross loans receivable acquired	62,500
Credit market adjustment of gross loans acquired	1,300
Costs related to the acquisition	$ 900
Number of Stores \| branch	4