Units Outstanding (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Changes in Limited Partnership Units Outstanding
Outstanding as of January 1, (in units)	272,301,827	273,040,452
Options exercised (in units)	358,262	541,073
Units issued (in units)	4,455,944	4,600,583
Units retired (in units)	(8,222,499)	(5,880,281)
Outstanding as of December 31, (in units)	268,893,534	272,301,827
AB Units [Member]
Changes in Limited Partnership Units Outstanding
Units retired (in units)	(15,998)	(26,111)