CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Capital in Excess of Par Value	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period of Adoption, Adjustment [Member]	Total
Balance at Dec. 31, 2017	$ 21,654			$ 906,745		$ (16,702)		$ 911,697
Balance (in shares) at Dec. 31, 2017	216,544,000
Increase (Decrease) in Stockholders' Equity
Stock issued for stock incentive plans, net	$ 37	$ 9,382						9,419
Stock issued for stock incentive plans, net (in shares)	367,000
Stock purchased and retired	$ (237)	(9,382)		(33,382)				(43,001)
Stock purchased and retired (in shares)	(2,367,000)
Net (loss) income				175,402				175,402
Pension adjustment, net of taxes						(1,408)		(1,408)
Foreign currency translation						(621)		(621)
Dividends declared				(101,069)				(101,069)
Balance at Dec. 31, 2018	$ 21,454			947,711		(18,746)		950,419
Balance (in shares) at Dec. 31, 2018	214,544,000
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)			$ 15		$ (15)
Stock issued for stock incentive plans, net	$ 66	8,564						8,630
Stock issued for stock incentive plans, net (in shares)	667,000
Stock purchased and retired	$ (77)	(8,564)		1,280				(7,361)
Stock purchased and retired (in shares)	(788,000)
Net (loss) income				(87,111)				(87,111)
Pension adjustment, net of taxes						(2,298)		(2,298)
Foreign currency translation						553		553
Dividends declared				(32,231)				(32,231)
Balance at Dec. 31, 2019	$ 21,443			832,113		(23,223)		$ 830,333
Balance (in shares) at Dec. 31, 2019	214,423,000							214,422,979
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)			$ 2,464		$ (2,732)		$ (268)
Stock issued for stock incentive plans, net	$ 71	8,664						$ 8,735
Stock issued for stock incentive plans, net (in shares)	716,000
Stock purchased and retired	$ (19)	$ (8,664)		7,857				(826)
Stock purchased and retired (in shares)	(188,000)
Net (loss) income				(212,192)				(212,192)
Pension adjustment, net of taxes						5,727		5,727
Foreign currency translation						(210)		(210)
Balance at Dec. 31, 2020	$ 21,495			$ 627,778		$ (17,706)		$ 631,567
Balance (in shares) at Dec. 31, 2020	214,951,000							214,951,093