Combined Guarantor Subsidiaries - Combined Statements of Owners' Equity - Summary (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Increase (Decrease) in Partners' Capital [Roll Forward]
Net loss	$ (92,034)			$ (2,971)			$ (168,531)	$ (33,608)
Guarantor Subsidiaries
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	1,416,003	$ 1,433,602	$ 1,404,623	1,499,229	$ 1,509,846	$ 1,486,164	1,404,623	1,486,164
Net loss	21,036	22,775	62,109	27,094	27,117	29,615	105,920	83,826
Contributions	23,971	16,558	17,363	14,164	14,677	50,514
Distributions	(67,143)	(54,312)	(41,658)	(114,838)	(52,411)	(56,447)
Noncash distributions		(2,620)	(8,835)
Ending balance	$ 1,393,867	$ 1,416,003	$ 1,433,602	$ 1,425,649	$ 1,499,229	$ 1,509,846	$ 1,393,867	$ 1,425,649