Statement of Partners' Capital (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Limited Partners' Capital Account, Units Outstanding	373,188,163	336,500,014	316,101,493
Net Income (Loss) Attributable to Parent	$ 1,339	$ 1,258	$ 1,316
Partners' Capital Account, Distributions	(2,560)	(2,243)	(1,827)
Non-cash compensation and severance expense allocated from General Partner	7	90	5
General Partners' Capital Account	2,860	259
Accumulated Other Comprehensive Income (Loss), Net of Tax	163	3	(186)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	107	267
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	44	(44)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	9	(34)
Stockholders' Equity Attributable to Parent	11,324	7,508	7,211
Stockholders' Equity Attributable to Noncontrolling Interest	255	96
Net Income (Loss) Attributable to Noncontrolling Interest	17	10	11
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	11,579	7,604	7,293
Common Units [Member]
Limited Partners' Capital Account, Units Outstanding	252,756,425	232,677,222	218,880,103	206,020,826
Limited Partners' Capital Account	4,723	4,347	4,282	4,058
Net Income (Loss) Attributable to Parent	(56)	57	299
Units issued as consideration pursuant to common unit compensation plan for non-employee directors		2,450	2,450
Stock Issued During Period, Value, Acquisitions	686	24	82
Stock Issued During Period, Shares, Acquisitions	8,661,627	324,961	1,287,287
Stock Issued During Period, Value, New Issues	909	955	759
Stock Issued During Period, Shares, New Issues	11,417,576	13,469,708	11,569,540
Partners' Capital Account, Distributions	(1,162)	(1,030)	(919)
Non-cash compensation and severance expense allocated from General Partner	4	61	3
Noncontrolling Interest, Increase from Equity Issuance or Sale of Parent Equity Interest	(4)
Partners' Capital, Other	(1)	(2)	0
Class B Units [Member]
Limited Partners' Capital Account, Units Outstanding	5,313,400	5,313,400	5,313,400	5,313,400
Limited Partners' Capital Account	14	42	63	78
Net Income (Loss) Attributable to Parent	(2)	2	8
Partners' Capital Account, Distributions	(26)	(24)	(23)
Non-cash compensation and severance expense allocated from General Partner		1
i-units [Member]
Limited Partners' Capital Account, Units Outstanding	115,118,338	98,509,392	91,907,990	85,538,266
Limited Partners' Capital Account	3,564	2,857	2,808	2,682
Net Income (Loss) Attributable to Parent	(20)	24	124
Stock Issued During Period, Value, New Issues	727
Distribution Made to Member or Limited Partner, Share Distribution	6,488,946	6,601,402	6,369,724
Stock Issued During Period, Shares, New Issues	10,120,000
Non-cash compensation and severance expense allocated from General Partner	1	26	2
Noncontrolling Interest, Increase from Equity Issuance or Sale of Parent Equity Interest	(1)
Partners' Capital, Other		(1)
General Partner [Member]
Net Income (Loss) Attributable to Parent	1,417	1,175	885
Partners' Capital Account, Distributions	(1,340)	(1,161)	(862)
Increase to general partner's capital account as a result of drop-down transaction	2,472
Non-cash compensation and severance expense allocated from General Partner		1
Partners' Capital Account, Contributions	45
Partners' Capital, Other	7
General Partners' Capital Account	2,860	259	244	221
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	163	3	(186)	(395)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	115	14	(75)
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(8)	253	187
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	44	(44)	99
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	9	(34)	(2)
Noncontrolling Interest [Member]
Non-cash compensation and severance expense allocated from General Partner	1	1
Noncontrolling Interest, Increase from Equity Issuance or Sale of Parent Equity Interest	84
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	2		(1)
Derivative Instruments, Gain (Loss) Recognized in Income, Net		3	2
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax		(1)	1
Stockholders' Equity Attributable to Noncontrolling Interest	255	96	82	80
Net Income (Loss) Attributable to Noncontrolling Interest	17	10	11
Contributions from Noncontrolling Interests	62	29	12
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(32)	(28)	(23)
Change in noncontrolling interest resulting from drop-down acquisition	$ 25