Derivative Instruments and Hedging Activities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	$ 86	$ 208
Total Liabilities at Fair Value	172	102
Accounts and notes receivable, net [Member] | Commodity [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	44	133
Long term receivables, net [Member] | Commodity [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	42	75
Accounts payable [Member] | Commodity [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	130	36
Deferred credits and other noncurrent obligations [Member] | Commodity [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	$ 42	$ 66