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 Income (Loss) [Member]
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
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
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	284,102
Cash flow hedges, net of tax	85,805
Balance, end of period at Jun. 30, 2022	1,843,551	$ 69,280	1,785,383	(62,074)	50,962
Balance, end of period (shares) at Jun. 30, 2022		69,280,000
Balance, beginning of period at Mar. 31, 2022	1,712,198	$ 69,372	1,782,940	(147,632)	7,518
Balance, beginning of period (shares) at Mar. 31, 2022		69,372,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	120,222			120,222
Shares issued for stock compensation		$ 3	(3)
Shares issued for stock compensation (shares)		3,000
Equity-based compensation expense	2,368		2,368
Repurchase of common stock	(4,156)	$ (95)		(4,061)
Repurchase of common stock (shares)		(95,000)
Pension plans and OPEB obligations, net of tax	915				915
Cash flow hedges, net of tax	42,529				42,529
Dividends on common stock	(30,524)			(30,524)
Other transactions, net	(1)		78	(79)
Balance, end of period at Jun. 30, 2022	1,843,551	$ 69,280	1,785,383	(62,074)	50,962
Balance, end of period (shares) at Jun. 30, 2022		69,280,000
Balance, beginning of period at Dec. 31, 2022	$ 2,263,153	$ 79,683	2,294,797	(208,979)	97,652
Balance, beginning of period (shares) at Dec. 31, 2022	79,683,000	79,683,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 16,260			16,260
Shares issued for stock compensation		$ 233	(233)
Shares issued for stock compensation (shares)		233,000
Equity-based compensation expense	2,279		2,279
Pension plans and OPEB obligations, net of tax	(131)				(131)
Cash flow hedges, net of tax	(17,335)				(17,335)
Dividends on common stock	(35,962)			(35,962)
Other transactions, net	(1)		84	(85)
Balance, end of period at Mar. 31, 2023	2,228,263	$ 79,916	2,296,927	(228,766)	80,186
Balance, end of period (shares) at Mar. 31, 2023		79,916,000
Balance, beginning of period at Dec. 31, 2022	$ 2,263,153	$ 79,683	2,294,797	(208,979)	97,652
Balance, beginning of period (shares) at Dec. 31, 2022	79,683,000	79,683,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 38,566
Cash flow hedges, net of tax	384
Balance, end of period at Jun. 30, 2023	$ 2,233,169	$ 79,911	2,298,593	(242,896)	97,561
Balance, end of period (shares) at Jun. 30, 2023	79,911,000	79,911,000
Balance, beginning of period at Mar. 31, 2023	$ 2,228,263	$ 79,916	2,296,927	(228,766)	80,186
Balance, beginning of period (shares) at Mar. 31, 2023		79,916,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,306			22,306
Shares issued for stock compensation		$ 4	(4)
Shares issued for stock compensation (shares)		4,000
Equity-based compensation expense	1,577		1,577
Repurchase of common stock	(394)	$ (9)		(385)
Repurchase of common stock (shares)		(9,000)
Pension plans and OPEB obligations, net of tax	(344)				(344)
Cash flow hedges, net of tax	17,719				17,719
Dividends on common stock	(35,958)			(35,958)
Other transactions, net			93	(93)
Balance, end of period at Jun. 30, 2023	$ 2,233,169	$ 79,911	$ 2,298,593	$ (242,896)	$ 97,561
Balance, end of period (shares) at Jun. 30, 2023	79,911,000	79,911,000