CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2016	$ 5,966	$ 128,455	$ 118,363	$ (30,206)	$ (14,543)	$ 208,035
Net income			25,014			25,014
Cash dividends			(10,675)			(10,675)
Stock dividend	558	75,108	(75,674)			(8)
Issuance of common shares pursuant to stock-based compensation plan, net		(821)		273		(548)
Exercise of SARs		(451)		142		(309)
Stock-based compensation expense		2,340				2,340
Purchase of common shares				(2,270)		(2,270)
Other comprehensive income (loss)					3,509	3,509
Other comprehensive income
reclassification for ASU 2018-02			2,286		(2,286)
Balance at Dec. 31, 2017	6,524	204,631	59,314	(32,061)	(13,320)	225,088
Net income			30,268			30,268
Cash dividends			(13,177)			(13,177)
Stock dividend	1,229		(1,234)			(5)
Issuance of common shares pursuant to stock-based compensation plan, net		(991)		624		(367)
Exercise of SARs		(876)		301		(575)
Stock-based compensation expense		3,006				3,006
Purchase of common shares				(8,838)		(8,838)
Other comprehensive income (loss)					(5,552)	(5,552)
Balance at Dec. 31, 2018	7,753	205,770	75,171	(39,974)	(18,872)	229,848
Net income			30,404			30,404
Cash dividends			(15,234)			(15,234)
Issuance of common shares pursuant to stock-based compensation plan, net		(1,417)		1,358		(59)
Exercise of SARs		(2,100)		1,034		(1,066)
Stock-based compensation expense		3,144				3,144
Purchase of common shares				(7,799)		(7,799)
Other comprehensive income (loss)					4,952	4,952
Balance at Dec. 31, 2019	$ 7,753	$ 205,397	$ 90,341	$ (45,381)	$ (13,920)	$ 244,190