LOANS AND LEASES - Nonaccrual, Restructured and Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Average current balance	$ 53,260	$ 50,383	$ 54,402	$ 52,443
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	15	62	67	224
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	293	259	941	710
Nonaccrual loans	30,118		30,118		$ 17,730
Accruing trouble debt restructurings	19,692		19,692		30,240
Total impaired loans	49,810		49,810		47,970
Restructured loans - nonaccrual status	9,100		9,100		5,100
Interest income effect
Gross amount of interest that would have been recorded under original terms	761	705	2,735	2,173
Interest included in income
Nonaccrual loans	140	97	445	269
Troubled debt restructurings	168	224	563	665
Total interest included in income	308	321	1,008	934
Net impact on interest income	453	384	1,727	1,239
Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	15,562	14,243	16,132	15,096
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	2	8	26	26
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	63	83	259	232
Nonaccrual loans	9,026		9,026		2,419
Total impaired loans	12,325		12,325		13,203
Interest included in income
Total interest included in income	65	91	285	258
Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	91	691	120	406
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	8
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	1	3	2
Nonaccrual loans	87		87		195
Total impaired loans	87		87		195
Interest included in income
Total interest included in income	1	1	3	10
Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	950	0	744	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	0	0	0	0
Nonaccrual loans	824		824		0
Total impaired loans	824		824		0
Interest included in income
Total interest included in income	0	0	0	0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	23,839	21,067	24,076	22,441
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	5	46	18	163
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	147	98	451	259
Nonaccrual loans	12,244		12,244		6,098
Total impaired loans	23,597		23,597		20,460
Interest included in income
Total interest included in income	152	144	469	422
Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	8,636	9,186	8,927	9,007
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	7	7	20	24
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	55	52	147	147
Nonaccrual loans	4,333		4,333		5,251
Total impaired loans	8,644		8,644		9,601
Interest included in income
Total interest included in income	62	59	167	171
Installment
Financing Receivable, Modifications [Line Items]
Average current balance	290	460	351	348
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	2	4	5
Nonaccrual loans	240		240		367
Total impaired loans	254		254		437
Interest included in income
Total interest included in income	1	2	4	5
Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	3,892	4,736	4,052	5,145
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	1	1	3	3
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	26	23	77	65
Nonaccrual loans	3,364		3,364		3,400
Total impaired loans	4,079		4,079		4,074
Interest included in income
Total interest included in income	27	24	80	68
Credit card
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	0		0		0
Loans with no related allowance recorded [member]
Financing Receivable, Modifications [Line Items]
Average current balance	49,608	40,515	49,199	41,864
Total impaired loans	47,959		47,959		37,383
Loans with no related allowance recorded [member] \| Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	13,730	13,015	14,669	13,990
Total impaired loans	12,146		12,146		12,134
Loans with no related allowance recorded [member] \| Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	91	155	120	138
Total impaired loans	87		87		195
Loans with no related allowance recorded [member] \| Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	950	0	744	0
Total impaired loans	824		824		0
Loans with no related allowance recorded [member] \| Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	23,187	14,363	21,563	14,757
Total impaired loans	23,089		23,089		12,232
Loans with no related allowance recorded [member] \| Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	7,569	7,887	7,801	7,587
Total impaired loans	7,581		7,581		8,412
Loans with no related allowance recorded [member] \| Installment
Financing Receivable, Modifications [Line Items]
Average current balance	290	460	351	348
Total impaired loans	254		254		437
Loans with no related allowance recorded [member] \| Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	3,791	4,635	3,951	5,044
Total impaired loans	3,978		3,978		3,973
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Modifications [Line Items]
Total impaired loans	1,851		1,851
Impaired Financing Receivables With Related Allowance [Member] \| Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	1,832	1,228	1,463	1,106
Total impaired loans	179		179		1,069
Impaired Financing Receivables With Related Allowance [Member] \| Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	0	536	0	268
Total impaired loans	0		0		0
Impaired Financing Receivables With Related Allowance [Member] \| Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	0	0	0	0
Total impaired loans	0		0		0
Impaired Financing Receivables With Related Allowance [Member] \| Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	652	6,704	2,513	7,684
Total impaired loans	508		508		8,228
Impaired Financing Receivables With Related Allowance [Member] \| Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	1,067	1,299	1,126	1,420
Total impaired loans	1,063		1,063		1,189
Impaired Financing Receivables With Related Allowance [Member] \| Installment
Financing Receivable, Modifications [Line Items]
Average current balance	0	0	0	0
Total impaired loans	0		0		0
Impaired Financing Receivables With Related Allowance [Member] \| Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	101	101	101	101
Total impaired loans	101		101		101
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Modifications [Line Items]
Average current balance	$ 3,652	$ 9,868	$ 5,203	$ 10,579
Total impaired loans					$ 10,587

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

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

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

+ Details

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

- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

+ Details

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

- 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

+ Details

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

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

+ Details

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

- Definition

Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82895541&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_ConsumerPortfolioSegmentMember
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=ffbc_OtherLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=ffbc_LoansWithNoRelatedAllowanceRecordedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=ffbc_ImpairedFinancingReceivablesWithRelatedAllowanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ffbc_ImpairedFinancingReceivablesAxis=ffbc_ImpairedFinancingReceivablesWithRelatedAllowanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: