XML 75 R60.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Statement of Accounting Policies - Additional Information (Detail) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) county Segment | Dec. 31, 2016 USD ($)
Summary Of Significant Accounting Policies [Line Items] |  |
Number of counties in which entity provides services | county | 15 |
Business segments | Segment | 1 |
Equity investments | 20.00% |
Loans past due days | 90 days |
Excess impaired credits | $ 100,000 |
Other liabilities | $ 3,900,000 |
Software purchases and developed are capitalized and amortized on straight-line basis | 7 years |
Guaranteed Minimum Death Benefit [Member] |  |
Summary Of Significant Accounting Policies [Line Items] |  |
Other liabilities |  | $ 3,300,000

X
- Definition Dollar threshold in which impaired credits are individually evaluated and reviewed. + References No definition available. + Details
Name: | fcf_ExcessImpairedLoanCredit
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loans Past Due Days + References No definition available. + Details
Name: | fcf_LoansPastDueDays
Namespace Prefix: | fcf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of Counties in Which Entity Provides Services + References No definition available. + Details
Name: | fcf_NumberofCountiesinWhichEntityProvidesServices
Namespace Prefix: | fcf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Equity investments in which ownership is at least 20% are accounted for using the "equity method" of accounting and are classified as 'Other Assets". + References No definition available. + Details
Name: | fcf_PercentageOfOwnershipInEquityInvestments
Namespace Prefix: | fcf_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Summary Of Significant Accounting Policies [Line Items] + References No definition available. + Details
Name: | fcf_SummaryOfSignificantAccountingPoliciesLineItems
Namespace Prefix: | fcf_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of capitalized software amortized on a straight-line basis. + References No definition available. + Details
Name: | fcf_UsefulLifeOfCapitalizedSoftware
Namespace Prefix: | fcf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accrued obligation to policyholders that relates to insured events for long-duration contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 25 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28366191&loc=d3e13145-158430 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(a)(1)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References No definition available. + Details
Name: | us-gaap_NumberOfOperatingSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_GuaranteedInsuranceContractTypeOfBenefitAxis=us-gaap_GuaranteedMinimumDeathBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |