Industry Segments - Corporate Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
General and administrative expense	$ 31,232	$ 27,181	$ 59,688	$ 60,792
Depreciation, amortization, and accretion	28,620	33,538	58,098	67,145
Other (income) expense, net	209	2,210	574	1,506
Warrants fair value adjustment			(11,521)	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	11,216	27,454	22,378	176,594
Interest expense, net	14,328	14,335	28,095	28,974
Corporate Overhead [Member]
Segment Reporting Information [Line Items]
General and administrative expense	12,051	8,021	21,606	17,950
Depreciation, amortization, and accretion	118	112	209	226
Other (income) expense, net	305	2,450	733	2,740
Warrants fair value adjustment	(5,545)	0	(11,521)	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	11,169	16,179	19,041	32,563
Interest expense, net	$ 4,240	$ 5,596	$ 8,014	$ 11,647