Units Outstanding (Details) - shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Units Outstanding
Outstanding as of December 31, 2017 (in units)	268,659,333
Options exercised (in units)	488,513	500,000
Units issued (in units)	2,471,307
Units retired (in units)	(1,396,739)
Balance as of June 30, 2018 (in units)	270,222,414
Limited Partners' Capital Account [Line Items]
Units purchased and retired (in units)	1,396,739
AB Units
Units Outstanding
Units retired (in units)	(3,750)
Limited Partners' Capital Account [Line Items]
Units purchased and retired (in units)	3,750