Combined Guarantor Subsidiaries - Combined Statements of Owners' Equity - Summary (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Increase (Decrease) in Partners' Capital [Roll Forward]
Net loss	$ (46,809)	$ (661)
Guarantor Subsidiaries
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	1,404,623	1,486,164
Net loss	62,109	29,615
Contributions	17,363	50,514
Distributions	(41,658)	(56,447)
Noncash distributions	(8,835)
Ending balance	$ 1,433,602	$ 1,509,846