Partners' Capital (Preferred Units) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Distributions		$ 8,838
Class C Preferred Units	$ 302,482		$ 281,688
Class B preferred units
Mezzanine equity, beginning balance		349,857	349,857
Amortization of discount			1,708
Distributions			23,247
Distributions paid			(17,675)
Class B Preferred Unit exchange			(357,137)
Mezzanine equity, ending balance
Class C preferred units
Mezzanine equity, beginning balance	281,688
Private placement of Class C Preferred Units			353,500
Discount			(104,250)
Amortization of discount	8,693		13,129
Distributions	12,101		19,309
Mezzanine equity, ending balance	302,482		$ 281,688
Deemed contribution from exchange	$ 103,800
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%