XML 60 R49.htm IDEA: XBRL DOCUMENT v3.10.0.1

Note 7 - Fair Value Measurements - Level 3 Fair Value Measurements (Details) - Valuation, Market Approach [Member]	Jun. 30, 2018	Dec. 31, 2017
Measurement Input, Discount Rate [Member] | Minimum [Member]
Discount rate	0.00055	0.00055
Measurement Input, Discount Rate [Member] | Maximum [Member]
Discount rate	0.000725	0.001325
Measurement Input, Discount Rate [Member] | Weighted Average [Member]
Discount rate	(0.000586)	0.000592
Measurement Input, Cost to Sell [Member] | Minimum [Member]
Level 3 Fair Value Measurements	0.000403	0.0002
Measurement Input, Cost to Sell [Member] | Maximum [Member]
Level 3 Fair Value Measurements	0.000639	0.000601
Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Level 3 Fair Value Measurements	(0.00061)	(0.000472)
Measurement Input, Discount for Lack of Marketability and Age of Appraisal [Member] | Minimum [Member]
Level 3 Fair Value Measurements	0.000236	0.000168
Measurement Input, Discount for Lack of Marketability and Age of Appraisal [Member] | Maximum [Member]
Level 3 Fair Value Measurements	0.003559	0.006833
Measurement Input, Discount for Lack of Marketability and Age of Appraisal [Member] | Weighted Average [Member]
Level 3 Fair Value Measurements	(0.000607)	(0.001107)

X

- Definition

Value of input used to measure impaired loans.

+ References

No definition available.

+ Details

Name:	nksh_ImpairedLoansMeasurementInput
Namespace Prefix:	nksh_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Value of input used to measure real estate owned by financial institution by financial institution which is not directly related to its business.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_OtherRealEstateOwnedMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_MarketApproachValuationTechniqueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputCostToSellMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_MeasurementInputTypeAxis=nksh_MeasurementInputDiscountForLackOfMarketabilityAndAgeOfAppraisalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: