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, 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	32.8	0	0	32.8
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	(13.5)	(0.2)	1.1	(12.6)
Balance at Mar. 31, 2012	12,620.6	(341.8)	109.5	12,388.3
Balance at Dec. 31, 2012	13,558.1	(370.4)	108.3	13,296.0
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	753.5	0	1.8	755.3
Cash distributions paid to limited partners	(577.6)	0	0	(577.6)
Cash distributions paid to noncontrolling interests	0	0	(2.4)	(2.4)
Net cash proceeds from issuance of common units	554.1	0	0	554.1
Amortization of fair value of equity-based awards	17.1	0	0	17.1
Cash flow hedges	0	(27.7)	0	(27.7)
Change in fair value of available-for-sale equity securities				0
Other	(24.6)	0	0	(24.6)
Balance at Mar. 31, 2013	$ 14,280.6	$ (398.1)	$ 107.7	$ 13,990.2