CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2019	$ 244,190	$ 7,753	$ 205,397	$ 90,341	$ (45,381)	$ (13,920)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,765			18,765
Cash dividends	(11,704)			(11,704)
Issuance of common shares pursuant to stock-based compensation plan, net	(1,040)		(2,378)		1,338
Exercise of SARs	(102)		(243)		141
Stock-based compensation expense	2,277		2,277
Purchase of common shares	(5,508)				(5,508)
Other comprehensive income (loss)	4,613					4,613
Ending balance at Sep. 30, 2020	251,491	7,753	205,053	97,402	(49,410)	(9,307)
Beginning balance at Jun. 30, 2020	248,527	7,753	204,258	95,514	(49,457)	(9,541)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,781			5,781
Cash dividends	(3,893)			(3,893)
Issuance of common shares pursuant to stock-based compensation plan, net	43		(4)		47
Stock-based compensation expense	799		799
Other comprehensive income (loss)	234					234
Ending balance at Sep. 30, 2020	251,491	7,753	205,053	97,402	(49,410)	(9,307)
Beginning balance at Dec. 31, 2020	261,160	7,753	204,875	99,062	(50,515)	(15)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,902			20,902
Cash dividends	(11,576)			(11,576)
Issuance of common shares pursuant to stock-based compensation plan, net	(752)		(2,932)		2,180
Exercise of SARs	(123)		(415)		292
Stock-based compensation expense	2,585		2,585
Purchase of common shares	(18,975)				(18,975)
Other comprehensive income (loss)	(5,578)					(5,578)
Ending balance at Sep. 30, 2021	247,643	7,753	204,113	108,388	(67,018)	(5,593)
Beginning balance at Jun. 30, 2021	260,767	7,753	203,098	105,398	(53,437)	(2,045)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,805			6,805
Cash dividends	(3,815)			(3,815)
Issuance of common shares pursuant to stock-based compensation plan, net	83		(51)		134
Exercise of SARs	0		0		0
Stock-based compensation expense	1,066		1,066
Purchase of common shares	(13,715)				(13,715)
Other comprehensive income (loss)	(3,548)					(3,548)
Ending balance at Sep. 30, 2021	$ 247,643	$ 7,753	$ 204,113	$ 108,388	$ (67,018)	$ (5,593)