XML 92 R77.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Benefit Plans - Additional Information (Detail) - USD ($) |  |  | 12 Months Ended
--- | --- | --- | ---
Mar. 08, 2018 | Jan. 01, 2000 | Dec. 31, 2017 | Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Minimum eligibility for full-time employees, age |  |  | 21 years |
Number of highest-paid consecutive years for benefits |  |  | 5 years |
Employer contributions |  |  | $ 1,800,000 | $ 0
Amount of accumulated benefit obligation for the defined benefit pension plan |  |  | $ 5,300,000 | 5,800,000
Percentage of first employee compensation for which company makes matching contribution |  |  | 1.00% |
Company contribution on employee specific contribution |  |  | 50.00% |
Number of hours in service required for the contribution to be allocated |  |  | 1000 hours |
Minimum eligibility for employees under 401(k) Plan age |  |  | 19 years |
Number of plan service years after which employer matching contribution vest |  |  | 2 years |
Expense attributable to the Plan amounted |  |  | $ 740,000 | 482,000
Percentage of vested participants |  | 100.00% |  |
Participants years of credited service |  | 2 years |  |
Compensation expense for ESOP |  |  | $ 0 | $ 0
Shares of the Company held by the ESOP (in shares) |  |  | 230,846 | 247,283
Minimum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Period of service credit by employee |  |  | 1 year |
Percentage of employee for which company makes specified contribution |  |  | 2.00% |
Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Percentage of employee for which company makes specified contribution |  |  | 6.00% |
Subsequent Event |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions | $ 205,000 |  |  |

X
- Definition Defined benefit pension plan minimum eligible age of employee. + References No definition available. + Details
Name: | fxnc_DefinedBenefitPensionPlanMinimumEligibleAgeOfEmployee
Namespace Prefix: | fxnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined contribution plan minimum eligible age of employee. + References No definition available. + Details
Name: | fxnc_DefinedContributionPlanMinimumEligibleAgeOfEmployee
Namespace Prefix: | fxnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined contribution plan percentage of employer matching contribution of first one percent of employee contribution. + References No definition available. + Details
Name: | fxnc_DefinedContributionPlanPercentageOfEmployerMatchingContributionOfFirstOnePercentOfEmployeeContribution
Namespace Prefix: | fxnc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined contribution plan stated percentage of employees contribution. + References No definition available. + Details
Name: | fxnc_DefinedContributionPlanStatedPercentageOfEmployeesContribution
Namespace Prefix: | fxnc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Employee matching contribution vesting period under plan. + References No definition available. + Details
Name: | fxnc_EmployeeMatchingContributionVestingPeriodUnderPlan
Namespace Prefix: | fxnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of highest paid consecutive periods of service for calculation of average compensation related to benefits. + References No definition available. + Details
Name: | fxnc_NumberOfHighestPaidConsecutivePeriodsOfServiceForCalculationOfAverageCompensationRelatedToBenefits
Namespace Prefix: | fxnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of service credit by employee. + References No definition available. + Details
Name: | fxnc_PeriodOfServiceCreditByEmployee
Namespace Prefix: | fxnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Services completed by eligible participant under plan. + References No definition available. + Details
Name: | fxnc_ServicesCompletedByEligibleParticipantUnderPlan
Namespace Prefix: | fxnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share based compensation arrangement by share based payment award vesting percentage under award requisite service period. + References No definition available. + Details
Name: | fxnc_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPercentageUnderAwardRequisiteServicePeriod
Namespace Prefix: | fxnc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of contribution received by defined benefit plan from employer which increases plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(ii) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(01) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of plan compensation cost recognized during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65895303&loc=d3e17540-113929 + Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Sum of the allocated, committed-to-be-released and suspense shares of the entity held by the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=65895303&loc=d3e17540-113929 + Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |