Units Outstanding (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Units Outstanding [Abstract]
Outstanding, Beginning of Period (in units)	278,115,232	274,745,592
Options exercised (in units)	86,543	486,017
Units issued (in units)	0	3,249,861
Limited Partners' Capital Account [Line Items]
Units retired (in units)	(354,187)	(365,410)
Units forfeited (in units)	0	(828)
Outstanding, End of Period (in units)	277,847,588	278,115,232
Limited Partners Capital Account Units [Member]
Limited Partners' Capital Account [Line Items]
Units retired (in units)	354,187	365,410