Financing receivable acquired loans.

No definition available.

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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

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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

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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

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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

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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=66008989&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=66008989&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 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 5: 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

+ 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=65884687&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=66008989&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

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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

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Loans (Details 4) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Ending allowance balance attributable to loans:
Individually evaluated for impairment	$ 96	$ 497
Collectively evaluated for impairment	10,603	8,450
Acquired loans	153	0
Total ending allowance balance	10,852	8,978	$ 7,632	$ 7,568
Loans:
Loans individually evaluated for impairment	7,338	10,082
Loans collectively evaluated for impairment	1,048,074	823,609
Acquired loans	370,359	460,959
Acquired with deteriorated credit quality	779,340	717,206
Loans	1,427,635	1,296,865
Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired with deteriorated credit quality	0	31
Loans:
Acquired with deteriorated credit quality	1,864	2,215
Commercial real estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment	44	429
Collectively evaluated for impairment	3,491	2,698
Acquired loans	42	0
Total ending allowance balance	3,577	3,127	2,676	2,752
Loans:
Loans individually evaluated for impairment	3,457	5,853
Loans collectively evaluated for impairment	376,632	297,087
Acquired loans	153,228	182,251
Loans	534,285	486,458
Commercial real estate \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	968	1,267
Commercial
Ending allowance balance attributable to loans:
Individually evaluated for impairment	4	5
Collectively evaluated for impairment	1,763	1,337
Acquired loans	107	0
Total ending allowance balance	1,874	1,373	1,420	1,219
Loans:
Loans individually evaluated for impairment	477	712
Loans collectively evaluated for impairment	195,146	156,415
Acquired loans	48,536	72,673
Loans	245,055	230,748
Commercial \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired with deteriorated credit quality	0	31
Loans:
Acquired with deteriorated credit quality	896	948
Residential real estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment	48	63
Collectively evaluated for impairment	2,153	1,782
Acquired loans	4	0
Total ending allowance balance	2,205	1,845	1,689	1,964
Loans:
Loans individually evaluated for impairment	3,308	3,414
Loans collectively evaluated for impairment	280,215	216,802
Acquired loans	146,672	174,366
Loans	430,195	394,582
Residential real estate \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired with deteriorated credit quality	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	2,766	2,160
Acquired loans	0	0
Total ending allowance balance	2,766	2,160	1,663	1,419
Loans:
Loans individually evaluated for impairment	96	103
Loans collectively evaluated for impairment	196,081	153,305
Acquired loans	21,923	31,669
Loans	218,100	185,077
Consumer \| Receivables Acquired with Deteriorated Credit Quality
Ending allowance balance attributable to loans:
Acquired with deteriorated credit quality	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	430	473
Acquired loans	0	0
Total ending allowance balance	430	473	$ 184	$ 214
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 with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	$ 0	$ 0