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, 2019	$ 5,142	$ 24,898	$ 43,954	$ 516	$ (803)	$ 73,707
Beginning balance, shares at Dec. 31, 2019	5,099,729
Net income			4,249			4,249
Other comprehensive income (loss)				3,311		3,311
Cash dividends			(3,358)			(3,358)
Stock-based compensation		94				94
Purchase of treasury stock					(1,372)	(1,372)
Purchase of treasury stock, shares	(83,877)
Treasury stock issued for stock plans		(6)			76	70
Treasury stock issued for stock plans, shares	4,459
Common stock issued for stock plans	$ 9	(9)
Common stock issued for stock plans, shares	9,530
Ending balance at Sep. 30, 2020	$ 5,151	24,977	44,845	3,827	(2,099)	76,701
Ending balance, shares at Sep. 30, 2020	5,029,841
Beginning balance at Dec. 31, 2019	$ 5,142	24,898	43,954	516	(803)	73,707
Beginning balance, shares at Dec. 31, 2019	5,099,729
Other comprehensive income (loss)				3,007
Ending balance at Dec. 31, 2020	$ 5,151	25,011	45,096	3,518	(2,179)	$ 76,597
Ending balance, shares at Dec. 31, 2020	5,025,441					5,025,441
Beginning balance at Jun. 30, 2020	$ 5,151	24,946	44,355	3,556	(1,106)	$ 76,902
Beginning balance, shares at Jun. 30, 2020	5,086,718
Net income			1,606			1,606
Other comprehensive income (loss)				271		271
Cash dividends			(1,116)			(1,116)
Stock-based compensation		31				31
Purchase of treasury stock					(993)	(993)
Purchase of treasury stock, shares	(56,877)
Ending balance at Sep. 30, 2020	$ 5,151	24,977	44,845	3,827	(2,099)	76,701
Ending balance, shares at Sep. 30, 2020	5,029,841
Beginning balance at Dec. 31, 2020	$ 5,151	25,011	45,096	3,518	(2,179)	$ 76,597
Beginning balance, shares at Dec. 31, 2020	5,025,441					5,025,441
Net income			5,271			$ 5,271
Other comprehensive income (loss)				(4,973)		(4,973)
Cash dividends			(3,304)			(3,304)
Stock-based compensation		110				110
Purchase of treasury stock					(675)	(675)
Purchase of treasury stock, shares	(39,198)
Treasury stock issued for stock plans		(161)			238	77
Treasury stock issued for stock plans, shares	13,783
Ending balance at Sep. 30, 2021	$ 5,151	24,960	47,063	(1,455)	(2,616)	$ 73,103
Ending balance, shares at Sep. 30, 2021	5,000,026					5,000,026
Beginning balance at Jun. 30, 2021	$ 5,151	24,922	46,266	26	(2,616)	$ 73,749
Beginning balance, shares at Jun. 30, 2021	5,000,026
Net income			1,897			1,897
Other comprehensive income (loss)				(1,481)		(1,481)
Cash dividends			(1,100)			(1,100)
Stock-based compensation		38				38
Ending balance at Sep. 30, 2021	$ 5,151	$ 24,960	$ 47,063	$ (1,455)	$ (2,616)	$ 73,103
Ending balance, shares at Sep. 30, 2021	5,000,026					5,000,026