LOANS - Nonaccrual, Restructured and Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	$ 11,908	$ 28,793	$ 25,919
Financing Receivable, Nonaccrual, No Allowance	16,715	19,599	54,833
Nonaccrual loans	28,623	48,392	80,752
Restructured loans - accrual status	11,000	11,600	7,100
Interest income effect
Gross amount of interest that would have been recorded under original terms	3,247	5,132	5,892
Interest included in income
Nonaccrual loans	1,134	1,618	1,636
Restructured loans	424	314	426
Impaired Financing Receivable, Interest Income, Accrual Method	1,558	1,932	2,062
Net impact on interest income	1,689	3,200	3,830
Loans and Leases Receivable-Nonaccrual, future commitment to lend	0	0	0
Restructured loans - nonaccrual status	10,000	16,000	14,700
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	6,692	11,077	18,711
Financing Receivable, Nonaccrual, No Allowance	1,550	6,285	10,519
Nonaccrual loans	8,242	17,362	29,230
Lease financing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	0	0	0
Financing Receivable, Nonaccrual, No Allowance	178	203	0
Nonaccrual loans	178	203	0
Construction real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	0	0	0
Financing Receivable, Nonaccrual, No Allowance	0	0	0
Nonaccrual loans	0	0	0
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	5,216	17,716	6,957
Financing Receivable, Nonaccrual, No Allowance	570	1,796	27,725
Nonaccrual loans	5,786	19,512	34,682
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	0	0	251
Financing Receivable, Nonaccrual, No Allowance	10,691	8,305	11,350
Nonaccrual loans	10,691	8,305	11,601
Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	0	0	0
Financing Receivable, Nonaccrual, No Allowance	3,123	2,922	5,076
Nonaccrual loans	3,123	2,922	5,076
Installment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Nonaccrual, With Allowance	0	0	0
Financing Receivable, Nonaccrual, No Allowance	603	88	163
Nonaccrual loans	$ 603	$ 88	$ 163

Financing Receivable, Impaired, Interest Income that would have been recorded

No definition available.

Name:	ffbc_FinancingReceivableImpairedInterestIncome
Namespace Prefix:	ffbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Financing Receivable, Impaired, Interest Income Recorded on Nonaccrual Loans

+ References

No definition available.

+ Details

Name:	ffbc_FinancingReceivableImpairedInterestIncomeRecordedOnNonaccrualLoans
Namespace Prefix:	ffbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Financing Receivable, Impaired, Interest Income Recorded on Restructured Loans

+ References

No definition available.

+ Details

Name:	ffbc_FinancingReceivableImpairedInterestIncomeRecordedOnRestructuredLoans
Namespace Prefix:	ffbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Financing Receivable, Nonaccrual, With Allowance

+ References

No definition available.

+ Details

Name:	ffbc_FinancingReceivableNonaccrualWithAllowance
Namespace Prefix:	ffbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the unfunded portion of contractual agreements to lend additional funds to borrowers whose loan is currently in a nonaccrual status.

+ References

No definition available.

+ Details

Name:	ffbc_LoansAndLeasesReceivableNonaccrualFutureCommitmentToLend
Namespace Prefix:	ffbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Restructured Loans, Accrual Status

+ References

No definition available.

+ Details

Name:	ffbc_RestructuredLoansAccrualStatus
Namespace Prefix:	ffbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Restructured Loans, Nonaccrual Status

+ References

No definition available.

+ Details

Name:	ffbc_RestructuredLoansNonaccrualStatus
Namespace Prefix:	ffbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

- Definition

Amortized cost of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

+ Details

Name:	us-gaap_FinancingReceivableNonaccrualNoAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (2)

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(2)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_FinanceLeasesPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: