XML 61 R53.htm IDEA: XBRL DOCUMENT
v3.20.1

Loans and Allowance for Credit Losses - Additional Information (Detail) - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2020 | Mar. 31, 2019 | Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Non Accrual Status Of Loans After Number Of Days Past Due | 90 days |  |
Default Status Of TDRs After Number Of Days Past Due | 90 days |  |
Unfunded commitments related to nonperforming loans | $ 3,700,000 |  | $ 1,700,000
Off balance sheet reserve to nonperforming loans | 23,000 |  | 12,000.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales | 0 | $ 0 |
Total gains or losses included in earnings | 0 | 0 |
Section4013LoanModifications | $ 1,100,000,000 |  |
Loans to individuals [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Non Accrual Status Of Loans After Number Of Days Past Due | 150 days |  |
Impaired Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans with modifications to rate and payment due to reamortization | $ 18,000 | $ 600,000 |
Nonaccrual Commercial Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans Held for sale, Amount | 0 |  | $ 0
Loans and Leases Receivable, Gain (Loss) on Sales, Net | $ 0 |  |

X
- Definition Default Status Of TDRs After Number Of Days Past Due + References No definition available. + Details
Name: | fcf_DefaultStatusOfTDRsAfterNumberOfDaysPastDue
Namespace Prefix: | fcf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Loans with modifications to rate and payment due to reamortization. + References No definition available. + Details
Name: | fcf_LoansWithModificationsToRateAndPaymentDueToReamortization
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Non Accrual Status Of Loans After Number Of Days Past Due + References No definition available. + Details
Name: | fcf_NonAccrualStatusOfLoansAfterNumberOfDaysPastDue
Namespace Prefix: | fcf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Off balance sheet reserve to nonperforming loans. + References No definition available. + Details
Name: | fcf_OffBalanceSheetReserveToNonperformingLoans
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Section4013LoanModifications + References No definition available. + Details
Name: | fcf_Section4013LoanModifications
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Unfunded commitments related to nonperforming loans. + References No definition available. + Details
Name: | fcf_UnfundedCommitmentsRelatedToNonperformingLoans
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- 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_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Reflects the net positive or negative amount derived from subtracting from net proceeds of sale and the carrying amounts, net of allocated reserves, of financial assets transferred to third parties in transactions that qualify for sales treatment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107425-111719 + Details
Name: | us-gaap_LoansAndLeasesReceivableGainLossOnSalesNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, before valuation allowance, of financing receivable classified as held-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 310 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=120238483&loc=d3e48678-111004 + Details
Name: | us-gaap_LoansReceivableHeldForSaleAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | fcf_LoanToDifferentProjectAxis=us-gaap_ConsumerLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=fcf_ImpairedLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fcf_NonaccrualCommercialLoansAxis=fcf_NonaccrualCommercialLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |