Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
NUMERATOR:
Net income	$ 503	$ 388	$ 1,600	$ 1,722
Incremental income effect of interest on 5.25% convertible notes	0	1	0	2
Net income after assumed conversion	$ 503	$ 389	$ 1,600	$ 1,724
DENOMINATOR:
Weighted-average shares outstanding, basic	597	618	605	630
Dilutive effect of Employee stock options and restricted stock units	1	1	1	2
Dilutive effect of 5.25% convertible notes	0	6	0	6
Adjusted weighted-average shares outstanding, diluted	598	625	606	638
NET INCOME PER SHARE:
Basic	$ 0.84	$ 0.63	$ 2.65	$ 2.73
Diluted	$ 0.84	$ 0.62	$ 2.64	$ 2.70