Earnings Per Share - Schedule of Computation for Earnings Per Share Types (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 1,224	$ 1,546	$ 1,827	$ 2,492
Basic weighted average shares outstanding, shares	728	758	728	766
Dilutive effect of share-based awards, shares	3	5	3	6
Diluted weighted average shares outstanding, shares	731	763	731	772
Basic earnings per share (in USD per share)	$ 1.68	$ 2.04	$ 2.51	$ 3.25
Diluted earnings per share (in USD per share)	$ 1.68	$ 2.03	$ 2.50	$ 3.23