Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Balance, beginning of period at Dec. 31, 2018	$ 1,314,779	$ 67,570	$ 1,659,031	$ (282,391)	$ (129,431)
Balance, beginning of period (shares) at Dec. 31, 2018		67,570
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	6,560			6,560
Shares issued for stock compensation		$ 297	(297)
Shares issued for stock compensation (shares)		297
Equity-based compensation expense	1,617		1,617
Pension plans and OPEB obligations	1,166				1,166
Cash flow hedges	(8,513)				(8,513)
Common dividends, $0.40 per share	(27,065)			(27,065)
Repurchase of common stock	$ (10,158)	$ (279)		(9,879)
Repurchase of common stock (shares)	(278,947)	(279)
Other transactions, net			99	(99)
Balance, end of period at Mar. 31, 2019	$ 1,278,386	$ 67,588	1,660,450	(312,874)	(136,778)
Balance, end of period (shares) at Mar. 31, 2019		67,588
Balance, beginning of period at Dec. 31, 2019	$ 1,226,831	$ 67,221	1,666,299	(359,330)	(147,359)
Balance, beginning of period (shares) at Dec. 31, 2019	67,221,000	67,221
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	$ (16,832)			(16,832)
Shares issued for stock compensation		$ 131	(131)
Shares issued for stock compensation (shares)		131
Equity-based compensation expense	1,885		1,885
Pension plans and OPEB obligations	15,578				15,578
Cash flow hedges	(38,525)				(38,525)
Common dividends, $0.40 per share	(26,941)			(26,941)
Repurchase of common stock	$ (12,355)	$ (401)		(11,954)
Repurchase of common stock (shares)	(400,917)	(401)
Other transactions, net	$ (27)		69	(96)
Balance, end of period at Mar. 31, 2020	$ 1,149,614	$ 66,951	$ 1,668,122	$ (415,153)	$ (170,306)
Balance, end of period (shares) at Mar. 31, 2020	66,951,000	66,951