Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Cash Flows from Operating Activities
Net income	$ 3,649	$ 3,779
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	59	203
Depreciation of bank premises and equipment	204	193
Amortization of intangibles	31	110
Amortization of premiums and accretion of discounts, net	17	26
Gain on sales and calls of securities available for sale, net		(6)
Gain on calls of securities held to maturity, net		(18)
Loss and write-down on other real estate owned, net	8	31
Increase in cash value of bank-owned life insurance	(143)	(147)
Originations of mortgage loans held for sale	(2,771)	(2,567)
Proceeds from sale of mortgage loans held for sale	2,676	3,185
Gain on sale of mortgage loans held for sale	(35)	(47)
Net change in:
Accrued interest receivable	(7)	182
Other assets	(1,570)	397
Accrued interest payable	(10)	6
Other liabilities	1,432	1,351
Net cash provided by operating activities	3,540	6,678
Cash Flows from Investing Activities
Net change in interest-bearing deposits	(5,284)	1,448
Proceeds from calls, principal payments, sales and maturities of securities available for sale	1,567	24,552
Proceeds from calls, principal payments and maturities of securities held to maturity	1,338	7,351
Purchases of securities available for sale		(53,360)
Net change in restricted stock	(30)	(41)
Purchases of loan participations	(487)	(440)
Collections of loan participations	14	15
Loan originations and principal collections, net	(4,231)	11,337
Proceeds from sale of other real estate owned	196	522
Recoveries on loans charged off	45	60
Proceeds from sale and purchases of premises and equipment, net	(26)	(14)
Net cash used in investing activities	(6,898)	(8,570)
Cash Flows from Financing Activities
Net change in time deposits	(6,325)	(7,087)
Net change in other deposits	9,363	6,740
Net cash provided by (used in) financing activities	3,038	(347)
Net change in cash and due from banks	(320)	(2,239)
Cash and due from banks at beginning of period	13,974	12,152
Cash and due from banks at end of period	13,654	9,913
Supplemental Disclosures of Cash Flow Information
Interest paid on deposits and borrowed funds	1,038	1,062
Income taxes paid
Supplemental Disclosure of Noncash Activities
Loans charged against the allowance for loan losses	143	453
Loans transferred to other real estate owned
Unrealized net gain on securities available for sale	$ 1,655	$ 5,144

This item represents the gain (loss) realized on held-to-maturity securities recalled by issuer of during the period.

No definition available.

Name:	nksh_HeldToMaturitySecuritiesRecalledSecurityRealizedGainLossExcludingOtherThanTemporaryImpairments
Namespace Prefix:	nksh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The difference between the sale price and the book value of a foreclosed asset that was sold or retired during the reporting period. Also included is the amount of any write-down or reserve provided in the period for other real estate owned. This element refers to the gain (loss) and/or write-down, and not to cash proceeds of the sale or write-down. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

No definition available.