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v3.23.1

Note 2 - Loans and Allowance for Credit Losses - Ratios of Allowance for Loan Losses (Details) | 3 Months Ended | 12 Months Ended
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Mar. 31, 2023 | Mar. 31, 2022 | Dec. 31, 2022
Ratio of ACLL to the end of period loans, net of unearned income and deferred fees and costs |  | 1.24% | 0.95% | 0.96%
Ratio of net charge-offs (recoveries), annualized, to average loans, net of unearned income and deferred fees and costs | [1] | (0.04%) | 0.01% | 0.02%
[1] | Net charge-offs are on an annualized basis.

X
- Definition Represents ratio of allowance for loan losses to the end of period loans, net of unearned income and deferred fees. + References No definition available. + Details
Name: | nksh_RatioOfAllowanceForLoanLossesToEndOfPeriodLoans
Namespace Prefix: | nksh_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents ratio of net charge-offs to average loans, net of unearned income and deferred fees. + References No definition available. + Details
Name: | nksh_RatioOfNetChargeoffsToAverageLoans
Namespace Prefix: | nksh_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration