Industry Segments - Corporate Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
General and administrative expense	$ 33,617	$ 29,460	$ 64,420	$ 56,211
Depreciation, amortization, and accretion	28,979	25,784	55,420	52,308
Other (income) expense, net	3,808	775	6,584	1,236
Warrants fair value adjustment			201	(11,521)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	12,132	7,966	33,189	12,211
Interest expense, net	18,379	14,328	33,352	28,095
Corporate Overhead [Member]
Segment Reporting Information [Line Items]
General and administrative expense	11,871	12,051	24,469	21,606
Depreciation, amortization, and accretion	164	118	315	209
Other (income) expense, net	220	305	370	733
Warrants fair value adjustment	2,195	(5,545)	201	(11,521)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	19,327	11,169	34,239	19,041
Interest expense, net	$ 4,877	$ 4,240	$ 8,884	$ 8,014