XML 80 R67.htm IDEA: XBRL DOCUMENT
v3.22.4

Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | $ 898,702 | $ 1,045,579
Gross Unrealized Gains | 275 | 9,515
Gross Unrealized Losses | (136,316) | (13,714)
Securities available for sale | 762,661 | 1,041,380
US States and Political Subdivisions Debt Securities [Member] |  |
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | 9,482 | 9,538
Gross Unrealized Gains | 0 | 89
Gross Unrealized Losses | (1,295) | (103)
Securities available for sale | 8,187 | 9,524
Corporate Securities [Member] |  |
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | 32,010 | 32,088
Gross Unrealized Gains | 179 | 973
Gross Unrealized Losses | (2,985) | (112)
Securities available for sale | 29,204 | 32,949
Obligations of U.S. Government-Sponsored Enterprises [Member] |  |
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | 527,800 |
Securities available for sale | 449,000 |
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage - Backed Securities - Residential [Member] |  |
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | 527,777 | 632,687
Gross Unrealized Gains | 59 | 6,308
Gross Unrealized Losses | (78,847) | (9,021)
Securities available for sale | 448,989 | 629,974
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member] |  |
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | 1,000 | 1,000
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (118) | (19)
Securities available for sale | 882 | 981
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Commercial [Member] |  |
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | 324,306 | 365,024
Gross Unrealized Gains | 0 | 1,725
Gross Unrealized Losses | (52,890) | (4,459)
Securities available for sale | 271,416 | 362,290
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Residential [Member] |  |
Investment Securities [Line Items] |  |
Total debt securities, Amortized Cost | 4,127 | 5,242
Gross Unrealized Gains | 37 | 420
Gross Unrealized Losses | (181) | 0
Securities available for sale | $ 3,983 | $ 5,662

X
- Definition Investment Securities [Line Items] + References No definition available. + Details
Name: | fcf_InvestmentSecuritiesLineItems
Namespace Prefix: | fcf_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of unrealized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesGrossUnrealizedGain
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesGrossUnrealizedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=fcf_OtherGovernmentSponsoredEnterprisesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |