Partners' Capital, Mezzanine Equity and Distributions (Change in Class A Convertible Preferred Units) (Details) - USD ($) $ in Thousands	1 Months Ended		6 Months Ended
	May 01, 2018	Jan. 31, 2018	Jun. 30, 2018
Mezzanine Capital Balance
Balance as of December 31, 2017		$ 697,151	$ 697,151
Balance as of June 30, 2018			$ 728,459
Number of Class A Convertible Preferred Units
Balance as of December 31, 2017		22,411,728	22,411,728
Balance as of June 30, 2018			23,402,956
Class A Convertible Preferred Stock Units
Mezzanine Capital Balance
Balance as of December 31, 2017		$ 697,151	$ 697,151
Distribution paid-in-kind	$ 16,900	$ 16,500	33,414
Allocation of Distribution paid in-kind to Preferred Distribution Rate Reset Election (Note 16)			(2,106)
Balance as of June 30, 2018			$ 728,459
Number of Class A Convertible Preferred Units
Balance as of December 31, 2017		22,411,728	22,411,728
Distribution paid-in-kind	500,976	490,252	991,228
Balance as of June 30, 2018			23,402,956