Fair Value Measurements (Assets And Liabilities That Are Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Money market funds	$ 3,104	$ 3,337
Available-for-sale investments	10	15
Derivatives, Assets	155	227
Total assets	3,269	3,579
Derivatives, Liabilities	(131)	(115)
Total liabilities	(131)	(115)
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Money market funds	3,104	3,337
Available-for-sale investments	5	10
Derivatives, Assets
Total assets	3,109	3,347
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Derivatives, Assets	155	227
Total assets	155	227
Derivatives, Liabilities	(131)	(115)
Total liabilities	(131)	(115)
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale investments	5	5
Total assets	$ 5	$ 5