Earnings Per Share - Schedule of Computation for Earnings Per Share Types (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
Earnings Per Share [Abstract]
Net income	$ 1,178	$ 1,259	$ 3,005	$ 3,751
Basic weighted average shares outstanding, shares	716	740	724	758
Dilutive effect of share-based awards, shares	3	4	3	4
Diluted weighted average shares outstanding, shares	719	744	727	762
Basic earnings per share (in USD per share)	$ 1.64	$ 1.70	$ 4.15	$ 4.95
Diluted earnings per share (in USD per share)	$ 1.64	$ 1.69	$ 4.13	$ 4.92