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, 2020	$ 1,304,953	$ 66,876	$ 1,674,576	$ (315,510)	$ (120,989)
Balance, beginning of period (shares) at Dec. 31, 2020		66,876,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	131,106			131,106
Shares issued for stock compensation		$ 166	(166)
Shares issued for stock compensation (shares)		166,000
Equity-based compensation expense	1,930		1,930
Pension plans and OPEB obligations, net of tax	2,953				2,953
Cash flow hedges, net of tax	64,107				64,107
Dividends on common stock	(27,484)			(27,484)
Other transactions, net	(16)		81	(97)
Balance, end of period at Mar. 31, 2021	1,477,549	$ 67,042	1,676,421	(211,985)	(53,929)
Balance, end of period (shares) at Mar. 31, 2021		67,042,000
Balance, beginning of period at Dec. 31, 2021	$ 1,526,133	$ 69,064	1,781,217	(280,910)	(43,238)
Balance, beginning of period (shares) at Dec. 31, 2021	69,064,000	69,064,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 163,880			163,880
Shares issued for stock compensation		$ 308	(308)
Shares issued for stock compensation (shares)		308,000
Equity-based compensation expense	2,056		2,056
Pension plans and OPEB obligations, net of tax	7,480				7,480
Cash flow hedges, net of tax	43,276				43,276
Dividends on common stock	(30,524)			(30,524)
Other transactions, net	(103)		(25)	(78)
Balance, end of period at Mar. 31, 2022	$ 1,712,198	$ 69,372	$ 1,782,940	$ (147,632)	$ 7,518
Balance, end of period (shares) at Mar. 31, 2022	69,372,000	69,372,000