Partners' Capital, Mezzanine Equity and Distributions (Change in Class A Convertible Preferred Units) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2018	Mar. 31, 2018
Mezzanine Capital Balance
Balance as of December 31, 2017	$ 697,151	$ 697,151
Balance as of March 31, 2018		$ 712,687
Number of Class A Convertible Preferred Units
Balance as of December 31, 2017	22,411,728	22,411,728
Balance as of March 31, 2018		22,901,980
Class A Convertible Preferred Stock Units
Mezzanine Capital Balance
Balance as of December 31, 2017	$ 697,151	$ 697,151
Distribution paid-in-kind	$ 16,500	16,527
Allocation of Distribution paid in-kind to Preferred Distribution Rate Reset Election (Note 16)		(991)
Balance as of March 31, 2018		$ 712,687
Number of Class A Convertible Preferred Units
Balance as of December 31, 2017	22,411,728	22,411,728
Distribution paid-in-kind	490,252	490,252
Balance as of March 31, 2018		22,901,980