Fair Value Measurements Footnote (details) - Financial Instruments - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Financial Instruments
Short-term securities	$ 4,671	$ 4,364
Commercial paper amount	100	100
Fair Value [Member]
Financial Instruments
Short-term securities	4,671	4,364
Debt	7,180	7,522
Commercial paper amount	100	100
Fair Value [Member] | Level 1 [Member]
Financial Instruments
Short-term securities	1,685	1,283
Fair Value [Member] | Level 2 [Member]
Financial Instruments
Short-term securities	2,958	3,042
Debt	7,180	7,522
Commercial paper amount	100	100
Fair Value [Member] | Level 3 [Member]
Financial Instruments
Short-term securities	28	39
Carrying Value [Member]
Financial Instruments
Short-term securities	4,671	4,364
Debt	6,244	6,249
Commercial paper amount	$ 100	$ 100