Consolidated Statements of Stockholders' Equity - 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		67,570,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	55,661			55,661
Equity-based compensation expense	7,272		7,272
Shares issued for stock compensation		$ 337	(337)
Shares issued for stock compensation (shares)		337,000
Repurchase of common stock	$ (25,173)	$ (686)		(24,487)
Repurchase of common stock (shares)	(686,240)	(686,000)
Pension plans and OPEB obligations	$ 512				512
Cash flow hedges	(18,440)				(18,440)
Common dividends	(107,722)			(107,722)
Other transactions, net	(58)		333	(391)
Balance, end of period at Dec. 31, 2019	1,226,831	$ 67,221	1,666,299	(359,330)	(147,359)
Balance, end of period (shares) at Dec. 31, 2019		67,221,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	166,830			166,830
Equity-based compensation expense	8,063		8,063
Shares issued for stock compensation		$ 144	(144)
Shares issued for stock compensation (shares)		144,000
Repurchase of common stock	$ (15,364)	$ (489)		(14,875)
Repurchase of common stock (shares)	(489,850)	(489,000)
Pension plans and OPEB obligations	$ 33,551				33,551
Cash flow hedges	(7,181)				(7,181)
Common dividends	(107,853)			(107,853)
Other transactions, net	76		358	(282)
Balance, end of period at Dec. 31, 2020	1,304,953	$ 66,876	1,674,576	(315,510)	(120,989)
Balance, end of period (shares) at Dec. 31, 2020		66,876,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	423,860			423,860
Equity-based compensation expense	8,607		8,607
Shares issued for stock compensation		$ 226	(226)
Shares issued for stock compensation (shares)		226,000
Shares issued for Loutre acquisition	$ 100,930	$ 1,962	98,968
Shares issued for Loutre acquisition (shares)		1,962,000
Repurchase of common stock (shares)	0
Pension plans and OPEB obligations	$ 42,439				42,439
Cash flow hedges	35,312				35,312
Common dividends	(388,241)			(388,241)
Other transactions, net	(1,727)		(708)	(1,019)
Balance, end of period at Dec. 31, 2021	$ 1,526,133	$ 69,064	$ 1,781,217	$ (280,910)	$ (43,238)
Balance, end of period (shares) at Dec. 31, 2021		69,064,000