Note 7 - Deposits (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Disclosure Text Block [Abstract]
Time Deposits, $250,000 or More	$ 23,188nksh_TimeDeposits250000OrMore	$ 25,885nksh_TimeDeposits250000OrMore
Deposit Liabilities Reclassified as Loans Receivable	$ 367	$ 315

Amount of deposits held by the entity that have been reclassified as loan balances receivable, for example, but not limited to, overdrafts receivable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 405

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6479006&loc=d3e64164-112818

Name:	us-gaap_DepositLiabilitiesReclassifiedAsLoansReceivable1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant