Computation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 2,220	$ 2,259	$ 1,936
Weighted average number of common shares (in shares)	799,217	804,680	748,010
Effect of dilutive outstanding equity-based awards (in shares)	11,760	10,236	9,755
Weighted average number of diluted common shares (in shares)	810,977	814,916	757,765
Basic EPS (in usd per share)	$ 2.78	$ 2.81	$ 2.59
Diluted EPS (in usd per share)	$ 2.74	$ 2.77	$ 2.56
Anti-dilutive awards (in shares)	210	5,609	8,620