Financing Receivable, Modified, Payment Deferral

No definition available.

Name:	fcf_FinancingReceivableModifiedPaymentDeferral
Namespace Prefix:	fcf_
Data Type:	dtr-types1:weightItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) in amortized cost excluding accrued interest, of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestModifiedIncreaseDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-33

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-34

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost of financing receivable with payment default in current period and modified within previous 12 months preceding payment default for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 44
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-44

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-34

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ContractualInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PrincipalForgivenessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=fcf_PaymentDeferralAndTermExtensionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_SeniorLienMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans and Allowance for Credit Losses - Loans Modified During the Period (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) Rate yr	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Rate yr	Sep. 30, 2022 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	$ 207		$ 632	$ 68
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage \| Rate	0.00%		0.01%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification \| Rate	0.00%		2.25%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	2 years 2 months 12 days		2 years 9 months 18 days
Financing Receivable, Excluding Accrued Interest, Modified, Increase (Decrease) from Modification	$ 0		$ 0
Financing Receivable, Modified, Payment Deferral \| yr	0.5		0.5
Financing Receivable, Troubled Debt Restructuring, Subsequent Default		$ 0	$ 0	0
Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	$ 0		22
Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	144		305
Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	0		0
Payment Deferral and Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	63		305
Residential real estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	$ 207		$ 632	68
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage \| Rate	0.01%		0.03%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification \| Rate	0.00%		2.25%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	2 years 2 months 12 days		2 years 9 months 18 days
Financing Receivable, Excluding Accrued Interest, Modified, Increase (Decrease) from Modification	$ 0		$ 0
Financing Receivable, Modified, Payment Deferral \| yr	0.5		0.5
Residential real estate [Member] \| Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	$ 0		$ 22
Residential real estate [Member] \| Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	144		305
Residential real estate [Member] \| Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	0		0
Residential real estate [Member] \| Payment Deferral and Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	63		305
Residential real estate [Member] \| Senior Lien
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	$ 207		$ 632	$ 68
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage \| Rate	0.01%		0.04%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification \| Rate	0.00%		2.25%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	2 years 2 months 12 days		2 years 9 months 18 days
Financing Receivable, Excluding Accrued Interest, Modified, Increase (Decrease) from Modification	$ 0		$ 0
Financing Receivable, Modified, Payment Deferral \| yr	0.5		0.5
Residential real estate [Member] \| Senior Lien \| Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	$ 0		$ 22
Residential real estate [Member] \| Senior Lien \| Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	144		305
Residential real estate [Member] \| Senior Lien \| Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	0		0
Residential real estate [Member] \| Senior Lien \| Payment Deferral and Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post- Modification Outstanding Recorded Investment	$ 63		$ 305