LOANS AND LEASES - Nonaccrual, Restructured and Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Average current balance	$ 43,429	$ 55,544
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	11	26
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	193	342
Nonaccrual loans	30,283		$ 24,082
Accruing trouble debt restructurings	14,943		17,545
Total impaired loans	45,226		41,627
Restructured loans - nonaccrual status	6,000		6,400
Interest income effect
Gross amount of interest that would have been recorded under original terms	802	816
Interest included in income
Nonaccrual loans	80	142
Troubled debt restructurings	124	226
Total interest included in income	204	368
Net impact on interest income	598	448
Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	8,071	16,701
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	13
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	26	109
Nonaccrual loans	6,275		5,229
Total impaired loans	8,810		7,331
Interest included in income
Total interest included in income	26	122
Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	41	149
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	0	1
Nonaccrual loans	0		82
Total impaired loans	0		82
Interest included in income
Total interest included in income	0	1
Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	28	538
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	0
Nonaccrual loans	26		29
Total impaired loans	26		29
Interest included in income
Total interest included in income	1	0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	23,139	24,313
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	3	5
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	99	160
Nonaccrual loans	16,878		10,616
Total impaired loans	24,736		21,542
Interest included in income
Total interest included in income	102	165
Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	7,554	9,218
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	7	7
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	47	46
Nonaccrual loans	3,324		4,140
Total impaired loans	7,175		7,932
Interest included in income
Total interest included in income	54	53
Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	4,315	4,212
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	1	1
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	20	24
Nonaccrual loans	3,484		3,743
Total impaired loans	4,173		4,456
Interest included in income
Total interest included in income	21	25
Installment
Financing Receivable, Modifications [Line Items]
Average current balance	281	413
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	0	2
Nonaccrual loans	296		243
Total impaired loans	306		255
Interest included in income
Total interest included in income	0	2
Loans with no related allowance recorded [member]
Financing Receivable, Modifications [Line Items]
Average current balance	40,334	48,790
Total impaired loans	43,482		37,183
Loans with no related allowance recorded [member] \| Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	7,867	15,607
Total impaired loans	8,571		7,162
Loans with no related allowance recorded [member] \| Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	41	149
Total impaired loans	0		82
Loans with no related allowance recorded [member] \| Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	28	538
Total impaired loans	26		29
Loans with no related allowance recorded [member] \| Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	21,400	19,939
Total impaired loans	24,377		18,423
Loans with no related allowance recorded [member] \| Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	6,503	8,033
Total impaired loans	6,130		6,876
Loans with no related allowance recorded [member] \| Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	4,214	4,111
Total impaired loans	4,072		4,356
Loans with no related allowance recorded [member] \| Installment
Financing Receivable, Modifications [Line Items]
Average current balance	281	413
Total impaired loans	306		255
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Modifications [Line Items]
Total impaired loans	1,744
Impaired Financing Receivables With Related Allowance [Member] \| Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	204	1,094
Total impaired loans	239		169
Impaired Financing Receivables With Related Allowance [Member] \| Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	0	0
Total impaired loans	0		0
Impaired Financing Receivables With Related Allowance [Member] \| Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	0	0
Total impaired loans	0		0
Impaired Financing Receivables With Related Allowance [Member] \| Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	1,739	4,374
Total impaired loans	359		3,119
Impaired Financing Receivables With Related Allowance [Member] \| Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	1,051	1,185
Total impaired loans	1,045		1,056
Impaired Financing Receivables With Related Allowance [Member] \| Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	101	101
Total impaired loans	101		100
Impaired Financing Receivables With Related Allowance [Member] \| Installment
Financing Receivable, Modifications [Line Items]
Average current balance	0	0
Total impaired loans	0		0
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Modifications [Line Items]
Average current balance	$ 3,095	$ 6,754
Total impaired loans			$ 4,444

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_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:

- 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: