Net Income (loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net income	$ 1,035	$ 482
Denominator:
Weighted average shares of common stock - basic	1,083	1,159
Dilutive effect of equity incentive awards (in shares)	19	11
Weighted average shares of common stock - diluted	1,102	1,170
Net income (loss) per share:
Net income per share - basic (in usd per share)	$ 0.96	$ 0.42
Net income per share - diluted (in usd per share)	$ 0.94	$ 0.41
Common stock equivalents excluded from income per diluted share because their effect would have been anti-dilutive (in shares)	1	6