Debt (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Short-term debt:
Commercial paper notes, bearing a weighted-average interest rate of 0.49% and 0.46%, respectively	$ 512	$ 734
Other short-term debt	3	3
Total short-term debt	915	1,287
Long-term debt:
Senior notes, net of unamortized discount of $16 and $18, respectively	8,759	8,757
Unamortized discount	16	18
Commercial paper notes, bearing a weighted-average interest rate of 0.49%	373
Long-term debt, other	5	5
Total long-term debt	9,137	8,762
Total debt	$ 10,052	$ 10,049
Commercial paper program
Short-term debt:
Weighted average interest rate, short-term (as a percent)	0.49%	0.46%
Long-term debt:
Weighted average interest rate, long-term (as a percent)	0.49%
5.25% senior notes due June 2015
Short-term debt:
Senior Notes, Current		$ 150
Long-term debt:
Debt instrument, interest rate (as a percent)		5.25%
3.95% senior notes due September 2015
Short-term debt:
Senior Notes, Current	$ 400	$ 400
Long-term debt:
Debt instrument, interest rate (as a percent)	3.95%	3.95%