Fair Value Measurements (Assets And Liabilities That Are Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Money market funds	$ 2,241	$ 3,104
Available-for-sale investments	8	10
Derivatives, Assets	129	155
Total assets	2,378	3,269
Derivatives, Liabilities	(124)	(131)
Total liabilities	(124)	(131)
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Money market funds	2,241	3,104
Available-for-sale investments	4	5
Total assets	2,245	3,109
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale investments
Derivatives, Assets	129	155
Total assets	129	155
Derivatives, Liabilities	(124)	(131)
Total liabilities	(124)	(131)
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale investments	4	5
Total assets	$ 4	$ 5