Fair Value Measurements Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	$ 12	$ 8
Derivatives, Assets	114	86
Derivatives, Liabilities	(53)	(79)
Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	2,676	3,783
Available-for-sale investments	12	8
Derivatives, Assets	114	86
Total assets	2,802	3,877
Derivatives, Liabilities	(53)	(79)
Total liabilities	(53)	(79)
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	2,676	3,783
Available-for-sale investments	12	6
Total assets	2,688	3,789
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, Assets	114	86
Total assets	114	86
Derivatives, Liabilities	(53)	(79)
Total liabilities	(53)	(79)
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		2
Total assets		$ 2