UNAUDITED CONDENSED STATEMENTS OF CONSOLIDATED EQUITY (USD $) In Millions, unless otherwise specified	Limited Partners [Member]	Accumulated Other Comprehensive Income Loss [Member]	Noncontrolling Interests [Member]	Total
Balance at Dec. 31, 2010	$ 11,406.7	$ (32.5)	$ 526.6	$ 11,900.8
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	420.7	0	13.8	434.5
Cash distributions paid to limited partners	(479.7)	0	0	(479.7)
Cash distributions paid to noncontrolling interests	0	0	(17.2)	(17.2)
Cash contributions from noncontrolling interests	0	0	1.3	1.3
Net cash proceeds from issuance of common units	21.0	0	0	21.0
Amortization of fair value of equity-based awards	12.0	0	0.1	12.1
Cash flow hedges	0	(66.9)	0	(66.9)
Change in fair value of available-for-sale equity securities				0
Other	(3.7)	(0.7)	(1.5)	(5.9)
Balance at Mar. 31, 2011	11,377.0	(100.1)	523.1	11,800.0
Balance at Dec. 31, 2011	12,464.8	(351.4)	105.9	12,219.3
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	651.3	0	4.2	655.5
Cash distributions paid to limited partners	(530.4)	0	0	(530.4)
Cash distributions paid to noncontrolling interests	0	0	(6.6)	(6.6)
Cash contributions from noncontrolling interests	0	0	4.9	4.9
Net cash proceeds from issuance of common units	29.0	0	0	29.0
Amortization of fair value of equity-based awards	15.6	0	0	15.6
Cash flow hedges	0	(6.0)	0	(6.0)
Change in fair value of available-for-sale equity securities	0	15.8	0	15.8
Other	(9.7)	(0.2)	1.1	(8.8)
Balance at Mar. 31, 2012	$ 12,620.6	$ (341.8)	$ 109.5	$ 12,388.3