Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	2,176	2,357
Other Assets, Fair Value Disclosure	344	341
Price Risk Derivatives, at Fair Value, Net	249	70
Interest Rate Derivatives, at Fair Value, Net	(66)	(91)
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net	123	(89)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	2,176	2,357
Other Assets, Fair Value Disclosure	344	341
Price Risk Derivatives, at Fair Value, Net	27	0
Interest Rate Derivatives, at Fair Value, Net	0	0
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Other Assets, Fair Value Disclosure	0	0
Price Risk Derivatives, at Fair Value, Net	222	70
Interest Rate Derivatives, at Fair Value, Net	(66)	(91)
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net	123	(89)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Other Assets, Fair Value Disclosure	0	0
Price Risk Derivatives, at Fair Value, Net	0	0
Interest Rate Derivatives, at Fair Value, Net	0	0
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net	0	0
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	958	958
Short-term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	958	958
Short-term Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Short-term Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Other Long-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	208	188
Other Long-term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	100	55
Other Long-term Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	27	24
Other Long-term Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	81	109
Cash and Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
Other Long-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).
Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).
Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).
Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.