CONSOLIDATED STATEMENT OF CHANGES IN PARTNERS' EQUITY (USD $) In Millions, unless otherwise specified	Total	Common Units	General Partner	Accumulated Other Comprehensive Loss
Partners' equity at Dec. 31, 2012	$ 1,301	$ 1,275	$ 27	$ (1)
Partners' equity (in units) at Dec. 31, 2012	53.5	53.5
Increase (Decrease) in Partners' Equity
Net income	29	28	1
Distributions paid	(43)	(42)	(1)
Partners' equity at Mar. 31, 2013	$ 1,287	$ 1,261	$ 27	$ (1)
Partners' equity (in units) at Mar. 31, 2013	53.5	53.5