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	52	51	1
Equity issuance, net (Note 6)	381	373	8
Equity issuance, net (Note 6) (in units)	8.8	8.8
Distributions paid	(85)	(83)	(2)
Partners' Equity at Jun. 30, 2013	$ 1,649	$ 1,616	$ 34	$ (1)
Partners' Equity (in units) at Jun. 30, 2013	62.3	62.3