Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 5,388	$ 3,985	$ 4,143
Net income attributable to noncontrolling interests	50	82	37
Preferred stock dividends	236	209	220
Preferred discount accretion and redemptions	26	6	5
Net income attributable to common shares	5,076	3,688	3,881
Dividends and undistributed earnings allocated to participating securities	23	26	17
Net Income (Loss) Available to Common Stockholders, Basic	5,053	3,662	3,864
Less: Impact of BlackRock earnings per share dilution	16	12	18
Net Income (Loss) Available to Common Stockholders, Diluted	$ 5,037	$ 3,650	$ 3,846
Weighted Average Number of Shares Outstanding, Basic (shares)	481	494	514
Basic earnings per common share (dollars per share)	$ 10.49	$ 7.42	$ 7.52
Dilutive potential common shares	5	6	7
Weighted Average Number of Shares Outstanding, Diluted (shares)	486	500	521
Diluted earnings per common share (dollars per share)	$ 10.36	$ 7.30	$ 7.39