Financial and Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Total Assets at Fair Value	$ 86	$ 208
Total Liabilities at Fair Value	149	102
Commodity Contract [Member] | Accounts and notes receivable, net [Member]
Derivatives, Fair Value [Line Items]
Total Assets at Fair Value	57	133
Commodity Contract [Member] | Long term receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total Assets at Fair Value	29	75
Commodity Contract [Member] | Accounts payable [Member]
Derivatives, Fair Value [Line Items]
Total Liabilities at Fair Value	112	36
Commodity Contract [Member] | Deferred credits and other noncurrent obligations [Member]
Derivatives, Fair Value [Line Items]
Total Liabilities at Fair Value	$ 37	$ 66