Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
NUMERATOR:
Net income	$ 820	$ 608	$ 1,333	$ 1,061
Incremental income effect of interest on 5.25% convertible notes	1	1	2	1
Net income after assumed conversion	$ 821	$ 609	$ 1,335	$ 1,062
DENOMINATOR:
Weighted-average shares outstanding, basic	632	665	637	670
Dilutive effect of Employee stock options and restricted stock units	1	2	1	2
Dilutive effect of 5.25% convertible notes	6	6	6	6
Adjusted weighted-average shares outstanding, diluted	639	673	644	678
NET INCOME PER SHARE:
Basic	$ 1.30	$ 0.91	$ 2.09	$ 1.58
Diluted	$ 1.28	$ 0.90	$ 2.07	$ 1.57