Financial and Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	$ 125	$ 413
Total Liabilities at Fair Value	75	84
Commodity [Member] | Accounts and notes receivable, net [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	120	401
Commodity [Member] | Long term receivables, net [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	5	12
Commodity [Member] | Accounts payable [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	71	57
Commodity [Member] | Deferred credits and other noncurrent obligations [Member]
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	$ 4	$ 27