CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Total
Balance at Dec. 31, 2019	$ 21,443		$ 832,113	$ (23,223)	$ 830,333
Balance (in shares) at Dec. 31, 2019	214,423
Increase (Decrease) in Stockholders' Equity
Stock issued for stock incentive plans, net	$ 100	$ 1,997			2,097
Stock issued for stock incentive plans, net (in shares)	1,014
Stock purchased and retired	$ (17)	(1,997)	1,222		(792)
Stock purchased and retired (in shares)	(177)
Net loss			(160,423)		(160,423)
Pension adjustment, net of taxes				732	732
Foreign currency translation				(712)	(712)
Balance at Mar. 31, 2020	$ 21,526		672,912	(23,203)	671,235
Balance (in shares) at Mar. 31, 2020	215,260
Balance at Dec. 31, 2019	$ 21,443		832,113	(23,223)	830,333
Balance (in shares) at Dec. 31, 2019	214,423
Increase (Decrease) in Stockholders' Equity
Net loss					(185,516)
Foreign currency translation					(398)
Balance at Jun. 30, 2020	$ 21,512		649,844	(22,703)	648,653
Balance (in shares) at Jun. 30, 2020	215,123
Balance at Mar. 31, 2020	$ 21,526		672,912	(23,203)	671,235
Balance (in shares) at Mar. 31, 2020	215,260
Increase (Decrease) in Stockholders' Equity
Stock issued for stock incentive plans, net	$ (4)	2,021			2,017
Stock issued for stock incentive plans, net (in shares)	(135)
Stock purchased and retired	$ (10)	(2,021)	2,025		(6)
Stock purchased and retired (in shares)	(2)
Net loss			(25,093)		(25,093)
Pension adjustment, net of taxes				186	186
Foreign currency translation				314	314
Balance at Jun. 30, 2020	$ 21,512		649,844	(22,703)	648,653
Balance (in shares) at Jun. 30, 2020	215,123
Balance at Dec. 31, 2020	$ 21,495		627,778	(17,706)	631,567
Balance (in shares) at Dec. 31, 2020	214,951
Increase (Decrease) in Stockholders' Equity
Stock issued for stock incentive plans, net	$ 93	1,446			1,539
Stock issued for stock incentive plans, net (in shares)	924
Stock purchased and retired	$ (14)	(1,446)	903		(557)
Stock purchased and retired (in shares)	(140)
Net loss			(9,662)		(9,662)
Pension adjustment, net of taxes				153	153
Foreign currency translation				136	136
Balance at Mar. 31, 2021	$ 21,574		619,019	(17,417)	623,176
Balance (in shares) at Mar. 31, 2021	215,735
Balance at Dec. 31, 2020	$ 21,495		627,778	(17,706)	631,567
Balance (in shares) at Dec. 31, 2020	214,951
Increase (Decrease) in Stockholders' Equity
Net loss					(10,388)
Foreign currency translation					205
Balance at Jun. 30, 2021	$ 21,573		619,756	(17,195)	624,134
Balance (in shares) at Jun. 30, 2021	215,725
Balance at Mar. 31, 2021	$ 21,574		619,019	(17,417)	623,176
Balance (in shares) at Mar. 31, 2021	215,735
Increase (Decrease) in Stockholders' Equity
Stock issued for stock incentive plans, net	$ (1)	1,472			1,471
Stock issued for stock incentive plans, net (in shares)	(9)
Stock purchased and retired		$ (1,472)	1,463		(9)
Stock purchased and retired (in shares)	(1)
Net loss			(726)		(726)
Pension adjustment, net of taxes				153	153
Foreign currency translation				69	69
Balance at Jun. 30, 2021	$ 21,573		$ 619,756	$ (17,195)	$ 624,134
Balance (in shares) at Jun. 30, 2021	215,725