Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Assets Measured on Recurring Basis, Cash and Cash Equivalents	$ 2,357		$ 2,696
Restricted cash equivalents and Short-term investments	341		440
Fair Value, Cash and Cash Equivalents, Valuation Techniques	(a)	[1]	(a)	[1]
Fair Value Assets Measured On Recurring Basis Restricted Cash Equivalents And Short Term Investments Valuation Techniques	(a)	[1]	(a)	[1]
Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	70		351
Fair Value, Derivative Assets, Valuation Techniques	(a)(c)	[1],[2]	(a)(c)	[1],[2]
Interest Rate Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	(91)		(74)
Fair Value, Derivative Assets, Valuation Techniques	(a)(c)	[1],[2]	(a)(c)	[1],[2]
Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	(89)		(96)
Fair Value, Derivative Assets, Valuation Techniques	(a)	[1]	(a)	[1]
Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	958		718
Fair Value, Investments, Valuation Techniques	(a)	[1]	(a)	[1]
Long Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	188		144
Fair Value, Investments, Valuation Techniques	(a)(c)	[1],[2]	(a)(c)	[1],[2]
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Assets Measured on Recurring Basis, Cash and Cash Equivalents	2,357		2,696
Restricted cash equivalents and Short-term investments	341		440
Fair Value, Inputs, Level 1 [Member] | Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0		0
Fair Value, Inputs, Level 1 [Member] | Interest Rate Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0		0
Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0		0
Fair Value, Inputs, Level 1 [Member] | Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	958		718
Fair Value, Inputs, Level 1 [Member] | Long Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	55		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Assets Measured on Recurring Basis, Cash and Cash Equivalents	0		0
Restricted cash equivalents and Short-term investments	0		0
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	70		351
Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	(91)		(74)
Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	(89)		(96)
Fair Value, Inputs, Level 2 [Member] | Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0		0
Fair Value, Inputs, Level 2 [Member] | Long Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	24		25
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Assets Measured on Recurring Basis, Cash and Cash Equivalents	0		0
Restricted cash equivalents and Short-term investments	0		0
Fair Value, Inputs, Level 3 [Member] | Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0		0
Fair Value, Inputs, Level 3 [Member] | Interest Rate Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0		0
Fair Value, Inputs, Level 3 [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0		0
Fair Value, Inputs, Level 3 [Member] | Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0		0
Fair Value, Inputs, Level 3 [Member] | Long Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 109		$ 119

[1] (a)Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities

[2] (c)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)