XML 70 R58.htm IDEA: XBRL DOCUMENT
v3.19.1

Benefit Plans (Detail) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 USD ($) payment | Mar. 31, 2018 USD ($) | Mar. 15, 2019 employee
Defined Benefit Plan Disclosure [Line Items] |  |  |
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 best | 2 years |  |
Expense attributable to the Plan amounted | $ 247 | $ 233 |
Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
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% |  |
Supplemental Executive Retirement Plans and Participation Agreements |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Expense attributable to the Plan amounted | $ 23 |  |
Number of employees | employee |  |  | 3
Number of monthly installments for retirement benefits payable | payment | 180 |  |

X
- Definition Defined Contribution Plan, Benefits Payable, Number Of Payments + References No definition available. + Details
Name: | fxnc_DefinedContributionPlanBenefitsPayableNumberOfPayments
Namespace Prefix: | fxnc_
Data Type: | xbrli:integerItemType
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 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 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 Number of employees eligible to participate in defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanNumberOfEmployees
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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_RetirementPlanTypeAxis=us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |