Derivative Instruments, Hedging Activities and Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended																																	1 Months Ended
	Sep. 30, 2012 Senior Notes AA [Member]	Sep. 30, 2012 Undesignated Swaps [Member]	Sep. 30, 2012 Future Debt Offering Tranche Three [Member]	Sep. 30, 2012 Natural gas processing: Forecasted natural gas purchases for plant thermal reduction (PTR) [Member] BillionscubicfeetBcf		Sep. 30, 2012 Natural gas processing: Forecasted sales of NGLs [Member] MMBbls		Sep. 30, 2012 Octane enhancement: Forecasted purchases of NGLs [Member] MMBbls		Sep. 30, 2012 Octane enhancement: Forecasted sales of octane enhancement products [Member] MMBbls		Sep. 30, 2012 Natural gas marketing: Forecasted sales of natural gas [Member] BillionscubicfeetBcf		Sep. 30, 2012 Natural gas marketing: Natural gas storage inventory management activities [Member] BillionscubicfeetBcf		Sep. 30, 2012 NGL marketing: Forecasted purchases of NGLs and related hydrocarbon products [Member] MMBbls		Sep. 30, 2012 NGL marketing: Forecasted sales of NGLs and related hydrocarbon products [Member] MMBbls		Sep. 30, 2012 Refined products marketing: Forecasted purchases of refined products [Member] MMBbls		Sep. 30, 2012 Refined products marketing: Forecasted sales of refined products [Member] MMBbls		Sep. 30, 2012 Crude oil marketing: Forecasted purchases of crude oil [Member] MMBbls		Sep. 30, 2012 Crude oil marketing: Forecasted sales of crude oil [Member] MMBbls		Sep. 30, 2012 Natural gas risk management activities [Member] BillionscubicfeetBcf		Sep. 30, 2012 Refined products risk management activities [Member] MMBbls		Sep. 30, 2012 Crude oil risk management activities [Member] MMBbls		Aug. 31, 2012 Derivatives in cash flow hedging relationships [Member] Forward Starting Swaps [Member]	Feb. 29, 2012 Derivatives in cash flow hedging relationships [Member] Forward Starting Swaps [Member]	Feb. 29, 2012 Derivatives in fair value hedging relationships [Member] Interest Rate Swap [Member]
Derivative [Line Items]
Number of Derivatives Outstanding	10	6	16
Type of Derivatives Outstanding	fixed-to-floating swaps	floating-to-fixed swaps	forward starting swaps
Notional Amount	$ 750.0	$ 600.0	$ 1,000.0
Period of Hedge	1/2011 to 2/2016	5/2010 to 7/2014
Expected Termination Date			3/2013
Rate Swap, fixed rate (in hundredths)	3.20%	2.00%
Rate Swap, floating rate (in hundredths)	1.40%	0.50%
Average Rate Locked (in hundredths)			3.70%
Current Volume				7.2	[1],[2],[3]	0.8	[1],[2],[4]	0.4	[1],[2]	2.3	[1],[2]	3.1	[1],[2]	14.5	[1],[2]	1.5	[1],[2]	4.4	[1],[2]	0.4	[1],[2]	0.8	[1],[2]	4.3	[1],[2]	6.2	[1],[2]	164.2	[1],[2],[5],[6]	1.1	[1],[2],[5]	5.1	[1],[2],[5]
Long Term Volume								0.4	[1],[2]	0.5	[1],[2]							0.1	[1],[2]					0.4	[1],[2]	0.9	[1],[2]	34.5	[1],[2],[5],[6]
Accounting Treatment	Fair value hedge	Mark-to-market	Cash flow hedge	Cash flow hedge	[3]	Cash flow hedge	[4]	Cash flow hedge		Cash flow hedge		Cash flow hedge		Fair value hedge		Cash flow hedge		Cash flow hedge		Cash flow hedge		Cash flow hedge		Cash flow hedge		Cash flow hedge		Mark-to-market	[5],[6]	Mark-to-market	[5]	Mark-to-market	[5]
Number of derivative instruments settled																																		7	10	11
Notional amount of settled derivative instruments																																		350	500	800
Loss (gain) recognized due to settlement of derivative instruments																																				$ (37.7)
Forecasted NGL sales designated as normal sales agreements						1.0
Current natural gas hedging volumes designated as an index plus or minus a discount																												49.3

[1] Volume for derivatives designated as hedging instruments reflects the total amount of volumes hedged whereas volume for derivatives not designated as hedging instruments reflects the absolute value of derivative notional volumes.

[2] The maximum term for derivatives designated as cash flow hedges, derivatives designated as fair value hedges and derivatives not designated as hedging instruments is December 2013, March 2013 and October 2015, respectively.

[3] PTR represents the British thermal unit ("Btu") equivalent of the NGLs extracted from natural gas by a processing plant, and includes the natural gas used as plant fuel to extract those liquids, plant flare and other shortages.

[4] Forecasted sales of NGL volumes under natural gas processing exclude 1.0 MMBbls of additional hedges executed under contracts that have been designated as normal sales agreements.

[5] Reflects the use of derivative instruments to manage risks associated with transportation, processing and storage assets.

[6] Current volumes include 49.3 Bcf of physical derivative instruments that are predominantly priced at an index plus a premium or minus a discount related to location differences.