Units Outstanding (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Units Outstanding
Outstanding as of December 31, 2018 (in units)	268,850,276
Options exercised (in units)	334,616	200,000
Units issued (in units)	381,305
Units retired (in units)	(2,380,095)
Balance as of March 31, 2019 (in units)	267,186,102
Limited Partners' Capital Account [Line Items]
Units purchased and retired (in units)	2,380,095
AB Units
Units Outstanding
Units retired (in units)	(300)
Limited Partners' Capital Account [Line Items]
Units purchased and retired (in units)	300