Financing receivable acquired loans.

No definition available.

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Namespace Prefix:	fmnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing receivable allowance for credit loss acquired with deteriorated credit quality.

+ References

No definition available.

+ Details

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Namespace Prefix:	fmnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

+ Details

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

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

+ Details

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

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section L
-Subsection 1

+ Details

Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5074-111524

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

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- Details

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Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Loans (Details 4) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Ending allowance balance attributable to loans:
Individually evaluated for impairment	$ 482	$ 497
Collectively evaluated for impairment	8,894	8,450
Acquired with deteriorated credit quality	14	31
Total ending allowance balance	9,390	8,978	$ 7,723	$ 7,632
Loans:
Loans individually evaluated for impairment	9,556	10,082
Loans collectively evaluated for impairment	862,198	823,609
Acquired loans	441,831	460,959
Acquired with deteriorated credit quality	724,870	716,721
Loans	1,315,501	1,296,865
Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired loans	0	0
Loans:
Acquired with deteriorated credit quality	1,916	2,215
Commercial real estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment	418	429
Collectively evaluated for impairment	2,763	2,698
Acquired with deteriorated credit quality	0	0
Total ending allowance balance	3,181	3,127	2,917	2,676
Loans:
Loans individually evaluated for impairment	5,444	5,853
Loans collectively evaluated for impairment	306,334	296,866
Acquired loans	178,030	181,987
Loans	490,789	485,973
Commercial real estate \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired loans	0	0
Loans:
Acquired with deteriorated credit quality	981	1,267
Commercial
Ending allowance balance attributable to loans:
Individually evaluated for impairment	5	5
Collectively evaluated for impairment	1,433	1,337
Acquired with deteriorated credit quality	14	31
Total ending allowance balance	1,452	1,373	1,351	1,420
Loans:
Loans individually evaluated for impairment	670	712
Loans collectively evaluated for impairment	167,728	156,415
Acquired loans	64,748	72,673
Loans	234,081	230,748
Commercial \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired loans	0	0
Loans:
Acquired with deteriorated credit quality	935	948
Residential real estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment	59	63
Collectively evaluated for impairment	1,855	1,782
Acquired with deteriorated credit quality	0	0
Total ending allowance balance	1,914	1,845	1,640	1,689
Loans:
Loans individually evaluated for impairment	3,354	3,414
Loans collectively evaluated for impairment	232,190	217,023
Acquired loans	170,053	174,630
Loans	405,597	395,067
Residential real estate \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired loans	0	0
Loans:
Acquired with deteriorated credit quality	0	0
Consumer
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,218	2,160
Acquired with deteriorated credit quality	0	0
Total ending allowance balance	2,218	2,160	1,705	1,663
Loans:
Loans individually evaluated for impairment	88	103
Loans collectively evaluated for impairment	155,946	153,305
Acquired loans	29,000	31,669
Loans	185,034	185,077
Consumer \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired loans	0	0
Loans:
Acquired with deteriorated credit quality	0	0
Unallocated
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	625	473
Acquired with deteriorated credit quality	0	0
Total ending allowance balance	625	473	$ 110	$ 184
Loans:
Loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	0	0
Acquired loans	0	0
Loans	0	0
Unallocated \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired loans	0	0
Loans:
Acquired with deteriorated credit quality	$ 0	$ 0