Partners' Capital (Preferred Units) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Mezzanine equity, beginning balance		$ 349,857
Distributions		17,675	$ 24,500
Mezzanine equity, ending balance				$ 349,857
Deemed contribution from exchange	$ 103,773	103,773
Class C preferred units, ending balance	262,113	262,113
Class B preferred units
Mezzanine equity, beginning balance		349,857	$ 343,912	343,912
Amortization of discount		1,708		2,358
Distributions		23,247		36,925
Distributions paid		(17,675)		(33,338)
Class B Preferred Unit exchange		(357,137)
Mezzanine equity, ending balance				$ 349,857
Class C preferred units
Deemed contribution from exchange		103,800
Private placement of Class C Preferred Units	353,500	353,500
Discount	(104,012)	(104,012)
Amortization of discount	5,050	5,050
Distributions	7,575	7,575
Class C preferred units, ending balance	$ 262,113	$ 262,113
Warrant exercise period		30 days
Class C preferred units | Distribution period commencing with the quarter ended on September 30, 2019
Distributions (as a percent)		12.50%
Class C preferred units | Distribution period commencing with the quarter ending March 31, 2022
Distributions (as a percent)		14.00%