Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
NUMERATOR:
Net income	$ 746	$ 820	$ 1,097	$ 1,333
Incremental income effect of interest on 5.25% convertible notes	0	1	0	2
Net income after assumed conversion	$ 746	$ 821	$ 1,097	$ 1,335
DENOMINATOR:
Weighted-average shares outstanding, basic	604	632	608	637
Dilutive effect of Employee stock options and restricted stock units	1	1	2	1
Dilutive effect of 5.25% convertible notes	0	6	0	6
Adjusted weighted-average shares outstanding, diluted	605	639	610	644
NET INCOME PER SHARE:
Basic	$ 1.24	$ 1.30	$ 1.80	$ 2.09
Diluted	$ 1.23	$ 1.28	$ 1.80	$ 2.07