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 (loss) 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, 2019	405,219	307,932	43,689	509,766	(91,726)	(364,442)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	19,738
Changes in fair market value of derivatives, net of tax	(2,861)
Changes in unrealized pension cost, net of tax	3,733
Cumulative translation adjustment, net of tax	(54)
Acquired shares for treasury stock	(8,080)
Ending Balance at Sep. 30, 2020	413,966	310,976	40,796	525,624	(90,908)	(372,522)
Beginning Balance at Mar. 31, 2020	397,466	310,098	39,832	512,276	(94,994)	(369,746)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	4,857			4,857
Changes in fair market value of derivatives, net of tax	644				644
Changes in unrealized pension cost, net of tax	1,209				1,209
Cumulative translation adjustment, net of tax	(14)				(14)
Cash dividends	(1,292)			(1,292)
Acquired shares for treasury stock	(2,776)					(2,776)
Issued shares on vesting of restricted stock units		855	(855)
Stock compensation	798		798
Ending Balance at Jun. 30, 2020	400,892	310,953	39,775	515,841	(93,155)	(372,522)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	11,073			11,073
Changes in fair market value of derivatives, net of tax	909				909
Changes in unrealized pension cost, net of tax	1,239				1,239
Cumulative translation adjustment, net of tax	99				99
Cash dividends	(1,290)			(1,290)
Issued shares on vesting of restricted stock units	(8)	23	(31)
Stock compensation	1,052		1,052
Ending Balance at Sep. 30, 2020	413,966	310,976	40,796	525,624	(90,908)	(372,522)
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 (loss) 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)
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 (loss) earnings	(51,031)
Changes in fair market value of derivatives, net of tax	100
Changes in unrealized pension cost, net of tax	90,976
Cumulative translation adjustment, net of tax	2
Acquired shares for treasury stock	(4,939)
Ending Balance at Sep. 30, 2021	457,374	314,351	40,958	484,368	(4,842)	(377,461)
Beginning Balance at Mar. 31, 2021	435,716	313,008	39,616	549,977	(94,363)	(372,522)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	875			875
Changes in fair market value of derivatives, net of tax	268				268
Changes in unrealized pension cost, net of tax	17,024				17,024
Cumulative translation adjustment, net of tax	1				1
Cash dividends	(1,299)			(1,299)
Issued shares on vesting of restricted stock units	(80)	1,333	(1,413)
Stock compensation	1,804		1,804
Ending Balance at Jun. 30, 2021	454,309	314,341	40,007	549,553	(77,070)	(372,522)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	(63,896)			(63,896)
Changes in fair market value of derivatives, net of tax	(292)				(292)
Changes in unrealized pension cost, net of tax	72,530				72,530
Cumulative translation adjustment, net of tax	(10)				(10)
Cash dividends	(1,289)			(1,289)
Acquired shares for treasury stock	(4,939)					(4,939)
Issued shares on vesting of restricted stock units	(10)	10	(20)
Stock compensation	971		971
Ending Balance at Sep. 30, 2021	$ 457,374	$ 314,351	$ 40,958	$ 484,368	$ (4,842)	$ (377,461)