Industry Segments - Corporate Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
General and administrative expense	$ 31,208	$ 28,589	$ 90,896	$ 89,381
Depreciation, amortization, and accretion	29,200	31,852	87,298	98,997
Other (income) expense, net	(668)	2,130	(94)	3,636
Warrants fair value adjustment			(11,568)	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	541	22,585	22,919	199,179
Interest expense, net	14,654	14,325	42,749	43,299
Corporate Overhead [Member]
Segment Reporting Information [Line Items]
General and administrative expense	12,277	8,748	33,883	26,698
Depreciation, amortization, and accretion	129	101	338	328
Other (income) expense, net	293	22	1,026	2,760
Warrants fair value adjustment	(47)	0	(11,568)	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	16,551	13,570	35,592	46,133
Interest expense, net	$ 3,899	$ 4,699	$ 11,913	$ 16,347