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Note 7 - Deposits (Tables) | 12 Months Ended
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Dec. 31, 2014
Disclosure Text Block [Abstract] |
Scheduled Maturities of Time Deposits [Table Text Block] |
2015 |  |  | 107,049 |
2016 |  |  | 59,857 |
2017 |  |  | 18,200 |
2018 |  |  | 22,550 |
2019 |  |  | 8,990 |
Thereafter |  |  | 100 |
|  | $ | 216,746 |

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- Definition Tabular disclosure of maturities of time deposits (including certificates of deposits, individual retirement accounts and open accounts) held by the entity. + References No definition available. + Details
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Namespace Prefix: | nksh_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_DisclosureTextBlockAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration