Derivative and Hedging Activities Netting Offsets (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term derivative assets	$ 50	$ 58
Long-term derivative assets ($1 and $0 attributable to our VIEs)	7	2
Short-term derivative liabilities	(54)	(105)
Long-term derivative liabilities	(546)	(934)
Short-term derivative instruments | Commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	159	110
Derivative Asset, Fair Value, Gross Liability	(109)	(52)
Derivative Asset, Fair Value, Net	50	58
Derivative Liability, Fair Value, Gross Asset	(163)	(157)
Derivative Liability, Fair Value, Gross Liability	109	52
Derivative Liability, Fair Value, Net	(54)	(105)
Short-term derivative instruments | 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	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative Liability, Fair Value, Net	0	0
Short-term derivative instruments | 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	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative Liability, Fair Value, Net	0	0
Long-term derivative instruments | Commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset	61	5
Derivative Asset, Fair Value, Gross Liability	(54)	(3)
Derivative Asset, Fair Value, Net	7	2
Derivative Liability, Fair Value, Gross Asset	(482)	(882)
Derivative Liability, Fair Value, Gross Liability	54	3
Derivative Liability, Fair Value, Net	(428)	(879)
Long-term derivative instruments | 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	(91)	(35)
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative Liability, Fair Value, Net	(91)	(35)
Long-term derivative instruments | 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	(27)	(20)
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative Liability, Fair Value, Net	$ (27)	$ (20)