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				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, 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				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