Units Outstanding (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Changes in Limited Partnership Units Outstanding
Outstanding as of January 1, (in units)	270,380,314	268,850,276
Options exercised (in units)	5,182	511,894
Units issued (in units)	3,363,132	4,833,715
Units retired (in units)	(3,238,970)	(3,815,571)
Outstanding as of December 31, (in units)	270,509,658	270,380,314
AB Units
Changes in Limited Partnership Units Outstanding
Units retired (in units)	(1,500)	(3,782)