Fair Value Measurements (Details) (USD $) In Millions	Jun. 30, 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	$ 2,612	$ 2,696
Restricted cash equivalents and Short-term investments	469	440
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	2,612	2,696
Restricted cash equivalents and Short-term investments	469	440
Fair Value, Inputs, Level 1 [Member] | Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	967	718
Fair Value, Inputs, Level 1 [Member] | Long Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
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 Currency Derivative Asset [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0	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] | 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	27	25
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	135	351
Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	(68)	(74)
Fair Value, Inputs, Level 2 [Member] | Foreign Currency Derivative Asset [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	(70)	(96)
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] | 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
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 Currency Derivative Asset [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	0	0
Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	967	718
Long Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	136	144
Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	135	351
Interest Rate Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	(68)	(74)
Foreign Currency Derivative Asset [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Hedge Derivatives	$ (70)	$ (96)