Units Outstanding (Details)	3 Months Ended
	Mar. 31, 2013
Limited Partners' Capital Account [Line Items]
Outstanding, Beginning of Period (in units)	277,600,901
Options exercised (in units)	392,528
Units issued (in units)	0
Units retired (in units)	(300)
Units forfeited (in units)	0
Outstanding, End of Period (in units)	277,993,129
AllianceBernstein Units [Member]
Limited Partners' Capital Account [Line Items]
Units retired (in units)	300