Fair Value Measurements Fair Value, Assets and Liabilities Measured on Recurring Basis (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]
Money market funds	$ 2,815	$ 3,104
Available-for-sale investments	9	10
Derivatives, Assets	162	155
Total assets	2,986	3,269
Derivatives, Liabilities	(94)	(131)
Total liabilities	(94)	(131)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	2,815	3,104
Available-for-sale investments	5	5
Total assets	2,820	3,109
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, Assets	162	155
Total assets	162	155
Derivatives, Liabilities	(94)	(131)
Total liabilities	(94)	(131)
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	4	5
Total assets	$ 4	$ 5