Derivative and Hedging Activities Netting Offsets Table (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term derivative assets	$ 11	$ 58
Long-term derivative assets	2	2
Short-term derivative liabilities	(170)	(105)
Long-term derivative liabilities	(519)	(934)
Commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	115	110
Derivative Asset, Fair Value, Gross Liability	(104)	(52)
Derivative Asset, Fair Value, Net	11	58
Short-term derivative assets		58
Interest rate contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset, Fair Value, Net	0	0
Foreign currency contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Asset, Fair Value, Net	0	0
Short [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term derivative liabilities	(170)
Short [Member] \| Commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Asset	(265)	(157)
Liability commodity contracts	104	52
Derivative Liability, Fair Value, Net	(161)	(105)
Short-term derivative liabilities		(105)
Short [Member] \| Interest rate contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Asset	(9)	0
Liability commodity contracts	0	0
Derivative Liability, Fair Value, Net	(9)	0
Short [Member] \| Foreign currency contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Liability, Fair Value, Gross Asset	0	0
Liability commodity contracts	0	0
Derivative Liability, Fair Value, Net	0	0
Long [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term derivative assets	2
Long [Member] \| Commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	11	5
Derivative Asset, Fair Value, Gross Liability	(9)	(3)
Derivative Asset, Fair Value, Net	2	2
Derivative Liability, Fair Value, Gross Asset	(444)	(882)
Liability commodity contracts	9	3
Derivative Liability, Fair Value, Net	(435)	(879)
Long-term derivative assets		2
Long-term derivative liabilities		(934)
Long [Member] \| Interest rate contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset, Fair Value, Net	0	0
Derivative Liability, Fair Value, Gross Asset	(79)	(35)
Liability commodity contracts	0	0
Derivative Liability, Fair Value, Net	(79)	(35)
Long [Member] \| Foreign currency contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset, Fair Value, Net	0	0
Derivative Liability, Fair Value, Gross Asset	(5)	(20)
Liability commodity contracts	0	0
Derivative Liability, Fair Value, Net	$ (5)	$ (20)

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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