CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - UNAUDITED - USD ($) $ in Thousands	Total	Common Stock	Additional Contributed Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning Balance at Dec. 31, 2019	$ 405,219	$ 307,932	$ 43,689	$ 509,766	$ (91,726)	$ (364,442)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	3,808			3,808
Changes in fair market value of derivatives, net of tax	(4,414)				(4,414)
Changes in unrealized pension cost, net of tax	1,285				1,285
Cumulative translation adjustment, net of tax	(139)				(139)
Cash dividends	(1,298)			(1,298)
Acquired shares for treasury stock	(5,304)					(5,304)
Issued shares on vesting of restricted stock units	(1,903)	2,166	(4,069)
Stock compensation	212		212
Ending Balance at Mar. 31, 2020	397,466	310,098	39,832	512,276	(94,994)	(369,746)
Beginning Balance at Dec. 31, 2020	423,682	311,190	41,654	539,281	(95,921)	(372,522)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	11,990			11,990
Changes in fair market value of derivatives, net of tax	124				124
Changes in unrealized pension cost, net of tax	1,422				1,422
Cumulative translation adjustment, net of tax	12				12
Cash dividends	(1,294)			(1,294)
Issued shares on vesting of restricted stock units	(1,400)	1,818	(3,218)
Stock compensation	1,180		1,180
Ending Balance at Mar. 31, 2021	$ 435,716	$ 313,008	$ 39,616	$ 549,977	$ (94,363)	$ (372,522)