XML 106 R93.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Interest-Bearing Deposits - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Deposits [Abstract] |  |  |
Interest-bearing demand deposit, money market | $ 1,200.0 |  |
Certificates of deposit in denominations of $100 thousand or more | 51.7 | $ 93.1 |
Interest expense related to certificates of deposit $100 thousand or greater | 0.4 | 2.0 | $ 3.3
Deposit Liabilities Reclassified as Loans Receivable | $ 0.6 | $ 0.7 |

X
- Definition Interest Expense, Time Deposits, $250,000 or More + References No definition available. + Details
Name: | fcf_InterestExpenseTimeDeposits250000orMore
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition TIme Deposits, $250,000 or More + References No definition available. + Details
Name: | fcf_TImeDeposits250000orMore
Namespace Prefix: | fcf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of deposits held by the entity that have been reclassified as loan balances receivable, for example, but not limited to, overdrafts receivable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 405 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=116652737&loc=d3e64164-112818 + Details
Name: | us-gaap_DepositLiabilitiesReclassifiedAsLoansReceivable1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DepositsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of interest-bearing domestic money market demand account deposit liabilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details
Name: | us-gaap_InterestBearingDomesticDepositMoneyMarket
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant