Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator:
Income from continuing operations	$ 482	$ 449
Income from discontinued operations, net of income taxes	0	177
Net income	$ 482	$ 626
Denominator:
Weighted average shares of common stock - basic	1,159	1,216
Dilutive effect of equity incentive awards (in shares)	11	13
Weighted average shares of common stock - diluted	1,170	1,229
Income per share - basic:
Continuing operations (in usd per share)	$ 0.42	$ 0.37
Discontinued operations (in usd per share)	0.00	0.14
Net income per share - basic (usd per share)	0.42	0.51
Income per share - diluted:
Continuing operations (in usd per share)	0.41	0.37
Discontinued operations (in usd per share)	0.00	0.14
Net income per share - diluted (in usd per share)	$ 0.41	$ 0.51
Common stock equivalents excluded from income per diluted share because their effect would have been anti-dilutive (in shares)	6	4