Reporting Segments - Reconciliation of Segment Operating Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of segment operating income to net income (loss):
Segment operating income (loss	$ 33,682	$ 1,322
General and administrative	(22,655)	(22,901)
Unit-based compensation expense	(3,373)	(1,941)
Interest expense, net	(8,341)	(5,093)
Gain on embedded derivative		47,794
Loss on earnout derivative	(2,353)
Other income (expense)	(2,353)	50
Net income (loss)	$ (3,040)	$ 19,231