CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Total
Balance at Dec. 31, 2017	$ 6,524	$ 204,631	$ 59,314	$ (32,061)	$ (13,320)	$ 225,088
Net income			23,211			23,211
Cash dividends			(9,342)			(9,342)
Issuance of common shares pursuant to stock-based compensation plan, net		(1,021)		614		(407)
Exercise of SARs		(877)		301		(576)
Stock-based compensation expense		2,238				2,238
Purchase of common shares				(883)		(883)
Other comprehensive income (loss)					(9,987)	(9,987)
Balance at Sep. 30, 2018	6,524	204,971	73,183	(32,029)	(23,307)	229,342
Balance at Jun. 30, 2018	6,524	204,687	68,771	(32,243)	(21,126)	226,613
Net income			7,610			7,610
Cash dividends			(3,198)			(3,198)
Issuance of common shares pursuant to stock-based compensation plan, net		(23)		63		40
Exercise of SARs		(454)		151		(303)
Stock-based compensation expense		761				761
Other comprehensive income (loss)					(2,181)	(2,181)
Balance at Sep. 30, 2018	6,524	204,971	73,183	(32,029)	(23,307)	229,342
Balance at Dec. 31, 2018	7,753	205,770	75,171	(39,974)	(18,872)	229,848
Net income			24,033			24,033
Cash dividends			(11,317)			(11,317)
Issuance of common shares pursuant to stock-based compensation plan, net		(1,426)		1,324		(102)
Exercise of SARs		(855)		464		(391)
Stock-based compensation expense		2,286				2,286
Purchase of common shares				(7,799)		(7,799)
Other comprehensive income (loss)					10,059	10,059
Balance at Sep. 30, 2019	7,753	205,775	87,887	(45,985)	(8,813)	246,617
Balance at Jun. 30, 2019	7,753	205,463	83,470	(46,333)	(9,932)	240,421
Net income			8,186			8,186
Cash dividends			(3,769)			(3,769)
Issuance of common shares pursuant to stock-based compensation plan, net		(5)		48		43
Exercise of SARs		(552)		300		(252)
Stock-based compensation expense		869				869
Other comprehensive income (loss)					1,119	1,119
Balance at Sep. 30, 2019	$ 7,753	$ 205,775	$ 87,887	$ (45,985)	$ (8,813)	$ 246,617