XML 63 R50.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Impairment of Investment Securities - Schedule of Unrealized Losses and Estimated Fair Values (Detail) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | $ 668,962 | $ 431,247
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (13,517) | (3,386)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 420,472 | 456,539
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (18,208) | (15,148)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 1,089,434 | 887,786
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (31,725) | (18,534)
US Government Agencies Residential Mortgage-backed Securities [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 7,923 | 5,584
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (190) | (21)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 7,923 | 5,584
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (190) | (21)
US Government Agency Debt Securities Commercial [Domain] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 95,862 | 48,322
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (2,120) | (962)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 31,813 | 32,683
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (1,356) | (894)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 127,675 | 81,005
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (3,476) | (1,856)
Residential Mortgage Backed Securities [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 500,625 | 351,222
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (10,277) | (2,295)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 378,709 | 400,984
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (15,836) | (9,746)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 879,334 | 752,206
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (26,113) | (12,041)
Obligations of U.S. Government-Sponsored Enterprises - Mortgage-Backed Securities - Commercial [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 13,560 | 13,985
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (299) | (71)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 13,560 | 13,985
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (299) | (71)
Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 999 | 997
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (1) | (1)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 99 | 99
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (1) | 0
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 1,098 | 1,096
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (2) | (1)
Obligations of States and Political Subdivisions [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 31,032 | 7,144
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (413) | (32)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 3,489 | 3,653
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (293) | (129)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 34,521 | 10,797
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (706) | (161)
Foreign Government Debt Securities [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 197 |
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (3) |
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 |
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 |
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 197 |
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | (3) |
Corporate Securities [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 18,764 | 3,993
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (214) | (4)
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 18,764 | 3,993
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | $ (214) | (4)
Pooled Trust Preferred Collateralized Debt Obligations [Member] |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |
Percent of Unrealized Losses | 2.00% |
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | $ 0 | 0
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 6,362 | 19,120
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (722) | (4,379)
Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total | 6,362 | 19,120
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss | $ (722) | $ (4,379)

X
- Definition Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss + References No definition available. + Details
Name: | fcf_InvestmentSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss + References No definition available. + Details
Name: | fcf_InvestmentSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment Securities, Continuous Unrealized Loss Position, Fair Value, Total + References No definition available. + Details
Name: | fcf_InvestmentSecuritiesContinuousUnrealizedLossPositionFairValueTotal
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss + References No definition available. + Details
Name: | fcf_InvestmentSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value + References No definition available. + Details
Name: | fcf_InvestmentSecuritiesContinuousUnrealizedLossPositionLessthanTwelveMonthsFairValue
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value + References No definition available. + Details
Name: | fcf_InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsorLongerFairValue
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Percent of Unrealized Losses + References No definition available. + Details
Name: | fcf_PercentOfUnrealizedLosses
Namespace Prefix: | fcf_
Data Type: | num:percentItemType
Balance Type: | na
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_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=fcf_USGovernmentAgencyDebtSecuritiesCommercialDomain
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

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

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=fcf_CorporateSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |