Fair Value Measurements Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivatives	$ 15	$ 25
Derivatives	(305)	(217)
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Money market funds	4,504	3,826
Commercial Paper, at Carrying Value	87
Available-for-sale Securities, Debt Securities	79
Available for Sale Securities, Government Agencies	83
Available-for-sale Securities, Equity Securities	20	7
Derivatives	15	25
Total assets	4,788	3,858
Derivatives	(305)	(217)
Total liabilities	(305)	(217)
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Money market funds	4,504	3,826
Available-for-sale Securities, Equity Securities	20	7
Total assets	4,524	3,833
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Commercial Paper, at Carrying Value	87
Available-for-sale Securities, Debt Securities	79
Available for Sale Securities, Government Agencies	83
Derivatives	15	25
Total assets	264	25
Derivatives	(305)	(217)
Total liabilities	$ (305)	$ (217)