CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Capital in Excess of Par Value	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings	Accumulated Other Comprehensive (Loss) Income Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive (Loss) Income	Cumulative Effect, Period of Adoption, Adjustment [Member]	Total
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,454			$ 947,711		$ (18,746)		$ 950,419
Balance at Dec. 31, 2018	$ 21,454			947,711		(18,746)		950,419
Balance (in shares) at Dec. 31, 2018	214,544
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,514		$ 2,376	927,556	$ (2,732)	(21,207)	$ (356)	927,863
Stock issued for stock incentive plans, net	$ 84	$ 2,368						2,452
Stock issued for stock incentive plans, net (in shares)	843
Stock purchased and retired	$ (24)	(2,368)		(306)				(2,698)
Stock purchased and retired (in shares)	(245)
Net (loss) income				(739)				(739)
Dividends				(21,486)				(21,486)
Pension adjustment, net of taxes						173		173
Foreign currency translation						98		98
Balance at Mar. 31, 2019	$ 21,514		2,376	927,556	(2,732)	(21,207)	(356)	927,863
Balance (in shares) at Mar. 31, 2019	215,142
Balance at Dec. 31, 2018	$ 21,454			947,711		(18,746)		950,419
Balance (in shares) at Dec. 31, 2018	214,544
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,450			854,170		(20,445)		855,175
Net (loss) income								(63,749)
Foreign currency translation								513
Balance at Sep. 30, 2019	$ 21,450			854,170		(20,445)		855,175
Balance (in shares) at Sep. 30, 2019	214,500
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,514		2,376	927,556	(2,732)	(21,207)	(356)	927,863
Balance at Mar. 31, 2019	$ 21,514		2,376	927,556	(2,732)	(21,207)	(356)	927,863
Balance (in shares) at Mar. 31, 2019	215,142
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,458		87	920,917	$ (2,732)	(20,700)	87	921,675
Stock issued for stock incentive plans, net	$ (2)	2,438						2,436
Stock issued for stock incentive plans, net (in shares)	(23)
Stock purchased and retired	$ (54)	(2,438)		(2,159)				(4,651)
Stock purchased and retired (in shares)	(540)
Net (loss) income				6,171				6,171
Dividends				(10,738)				(10,738)
Pension adjustment, net of taxes						174		174
Foreign currency translation						333		333
Balance at Jun. 30, 2019	$ 21,458		87	920,917		(20,700)	87	921,675
Balance (in shares) at Jun. 30, 2019	214,579
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,458		87	920,917		(20,700)	87	921,675
Adoption of accounting standard (Note 1)	21,450		$ 87	854,170		(20,445)	$ 87	855,175
Stock issued for stock incentive plans, net	$ (8)	2,444						2,436
Stock issued for stock incentive plans, net (in shares)	(77)
Stock purchased and retired		(2,444)		2,434				(10)
Stock purchased and retired (in shares)	(2)
Net (loss) income				(69,181)				(69,181)
Pension adjustment, net of taxes						173		173
Foreign currency translation						82		82
Balance at Sep. 30, 2019	$ 21,450			854,170		(20,445)		855,175
Balance (in shares) at Sep. 30, 2019	214,500
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,450			854,170		(20,445)		855,175
Adoption of accounting standard (Note 1)	21,443			832,113		(23,223)		830,333
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
Adoption of accounting standard (Note 1)	$ 21,526			672,912		(23,203)		671,235
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) income				(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
Adoption of accounting standard (Note 1)	$ 21,507			638,590		(22,542)		830,333
Net (loss) income								(201,953)
Foreign currency translation								(423)
Balance at Sep. 30, 2020	$ 21,507			638,590		(22,542)		637,555
Balance (in shares) at Sep. 30, 2020	215,067
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,526			672,912		(23,203)		671,235
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
Adoption of accounting standard (Note 1)	$ 21,512			649,844		(22,703)		648,653
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) income				(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
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,512			649,844		(22,703)		648,653
Adoption of accounting standard (Note 1)	21,507			638,590		(22,542)		648,653
Stock issued for stock incentive plans, net	$ (5)	5,212						5,207
Stock issued for stock incentive plans, net (in shares)	(54)
Stock purchased and retired		$ (5,212)		5,183				(29)
Stock purchased and retired (in shares)	(2)
Net (loss) income				(16,437)				(16,437)
Pension adjustment, net of taxes						186		186
Foreign currency translation						(25)		(25)
Balance at Sep. 30, 2020	$ 21,507			638,590		(22,542)		637,555
Balance (in shares) at Sep. 30, 2020	215,067
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standard (Note 1)	$ 21,507			$ 638,590		$ (22,542)		$ 637,555