Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
NUMERATOR:
Net income	$ 608	$ 465	$ 1,061	$ 617
Incremental income effect of interest on 5.25% convertible notes	1	1	1	2
Net income after assumed conversion	$ 609	$ 466	$ 1,062	$ 619
DENOMINATOR:
Weighted-average shares outstanding, basic	665	690	670	694
Dilutive effect of Employee stock options and restricted stock units	2	2	2	3
Dilutive effect of 5.25% convertible notes	6	6	6	6
Adjusted weighted-average shares outstanding, diluted	673	698	678	703
NET INCOME PER SHARE:
Basic	$ 0.91	$ 0.67	$ 1.58	$ 0.89
Diluted	$ 0.90	$ 0.67	$ 1.57	$ 0.88