XML 56 R46.htm IDEA: XBRL DOCUMENT v3.23.1

Note 5 - Fair Value Measurements - Change in Fair Value Measurement Impacts Net Income (Details) - Valuation, Market Approach [Member]	Mar. 31, 2023
Pull-through Rate [Member] | Weighted Average [Member] | Interest Rate Contract [Member]
Derivative asset (liability)	0.8130
Pull-through Rate [Member] | Weighted Average [Member] | Forward Contract [Member]
Derivative asset (liability)	0.8130
Current Reference Price [Member] | Weighted Average [Member] | Interest Rate Contract [Member]
Derivative asset (liability)	(1.0124)
Current Reference Price [Member] | Weighted Average [Member] | Forward Contract [Member]
Derivative asset (liability)	(1.0124)
Current Reference Price [Member] | Minimum [Member] | Interest Rate Contract [Member]
Derivative asset (liability)	1.0083
Current Reference Price [Member] | Minimum [Member] | Forward Contract [Member]
Derivative asset (liability)	1.0083
Current Reference Price [Member] | Maximum [Member] | Interest Rate Contract [Member]
Derivative asset (liability)	1.0222
Current Reference Price [Member] | Maximum [Member] | Forward Contract [Member]
Derivative asset (liability)	1.0222

X

- Definition

Value of input used to measure net derivative asset (liability).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

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

X

- Details

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

X

- Details

Name:	us-gaap_MeasurementInputTypeAxis=nksh_PullthroughRateMember
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_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=nksh_ForwardContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_MeasurementInputTypeAxis=nksh_CurrentReferencePriceMember
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:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: