Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Income from continuing operations	$ 310	$ 720	$ 1,234	$ 1,765
Income (loss) from discontinued operations, net of income taxes	0	1	(4)	5
Net income	$ 310	$ 721	$ 1,230	$ 1,770
Denominator:
Weighted average shares of common stock - basic (in shares)	830	974	863	992
Dilutive effect of equity incentive awards (in shares)	7	9	7	13
Weighted average shares of common stock - diluted (in shares)	837	983	870	1,005
Income per share - basic:
Continuing operations (in usd per share)	$ 0.37	$ 0.74	$ 1.43	$ 1.78
Discontinued operations (in usd per share)	0	0	0	0
Net income per share - basic (in usd per share)	0.37	0.74	1.43	1.78
Income per share - diluted:
Continuing operations (in usd per share)	0.37	0.73	1.42	1.76
Discontinued operations (in usd per share)	0	0	0	0
Net income per share - diluted (in usd per share)	$ 0.37	$ 0.73	$ 1.42	$ 1.76
Common stock equivalents excluded from income per diluted share because their effect would have been anti-dilutive (in shares)	6	15	19	12