Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Total
Beginning balance at Dec. 31, 2016	$ 4,805	$ 18,476	$ 39,945	$ (3,209)	$ (927)	$ 59,090
Beginning balance, shares at Dec. 31, 2016	4,755,630
Net income			3,959			3,959
Other comprehensive loss				370		370
Cash dividends per share			(3,145)			(3,145)
Stock-based compensation		54				54
Purchase of treasury stock					(86)	(86)
Purchase of treasury stock, shares	(4,289)
Treasury stock issued for stock plans		(10)			182	172
Treasury stock issued for stock plans, shares	9,704
Common stock issued for stock plans	$ 6	28				34
Common stock issued for stock plans, shares	6,611
Ending balance at Sep. 30, 2017	$ 4,811	18,548	40,759	(2,839)	(831)	60,448
Ending balance, shares at Sep. 30, 2017	4,767,656
Beginning balance at Dec. 31, 2017	$ 4,811	18,565	40,876	(4,034)	(831)	$ 59,387
Beginning balance, shares at Dec. 31, 2017	4,767,656					4,767,656
Net income			4,281			$ 4,281
Other comprehensive loss				(1,612)		(1,612)
Reclassification for ASU 2016-01			156	(156)
Cash dividends per share			(3,290)			(3,290)
Stock-based compensation		60				60
Purchase of treasury stock					(40)	(40)
Purchase of treasury stock, shares	(1,928)
Treasury stock issued for stock plans		(7)			98	91
Treasury stock issued for stock plans, shares	5,170
Common stock issued for stock plans	$ 8	34				42
Common stock issued for stock plans, shares	7,354
Common stock issued for acquisition	$ 315	6,148				6,463
Common stock issued acquisition, shares	315,284
Ending balance at Sep. 30, 2018	$ 5,134	$ 24,800	$ 42,023	$ (5,802)	$ (773)	$ 65,382
Ending balance, shares at Sep. 30, 2018	5,093,536					5,093,536