Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 1,996	$ 2,357
Other Assets, Fair Value Disclosure	400	341
Price Risk Derivatives, at Fair Value, Net	252	70
Interest Rate Derivatives, at Fair Value, Net	(70)	(91)
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net	(33)	(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	1,996	2,357
Other Assets, Fair Value Disclosure	400	341
Price Risk Derivatives, at Fair Value, Net	50	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	202	70
Interest Rate Derivatives, at Fair Value, Net	(70)	(91)
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net	(33)	(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	959	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	959	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	209	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	94	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	26	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	$ 89	$ 109