Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Capital Stock [Member]	Surplus [Member]	Undivided Profits [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2018	$ 100,175	$ 176,710	$ 256,397	$ (10,309)	$ (33,102)	$ 489,871
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	14,558	0	0	14,558
Other comprehensive income, net of tax	0	0	0	3,298	0	3,298
Stock options exercised	5	30	0	0	0	35
Cash dividend declared	0	0	(6,591)	0	0	(6,591)
Purchase of treasury stock	0	0	0	0	(35)	(35)
Sale of treasury stock	0	(218)	0	0	812	594
Stock based compensation expense	0	(12)	0	0	0	(12)
Balance at Mar. 31, 2019	100,180	176,510	264,364	(7,011)	(32,325)	501,718
Balance at Dec. 31, 2019	100,205	176,427	288,067	4,461	(30,903)	538,257
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	13,313	0	0	13,313
Other comprehensive income, net of tax	0	0	0	6,931	0	6,931
Cash dividend declared	0	0	(6,827)	0	0	(6,827)
Purchase of treasury stock	0	0	0	0	(3,493)	(3,493)
Stock based compensation expense	0	4	0	0	0	4
Balance at Mar. 31, 2020	$ 100,205	$ 176,431	$ 294,553	$ 11,392	$ (34,396)	$ 548,185