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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 1,259	$ 1,315	$ 3,751	$ 3,546
Basic weighted average shares outstanding, shares	740	788	758	803
Dilutive effect of share-based awards, shares	4	7	4	8
Diluted weighted average shares outstanding, shares	744	795	762	811
Basic earnings per share (in USD per share)	$ 1.70	$ 1.67	$ 4.95	$ 4.42
Diluted earnings per share (in USD per share)	$ 1.69	$ 1.65	$ 4.92	$ 4.37