Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 1,271	$ 1,239
Net income attributable to noncontrolling interests	10	10
Preferred stock dividends	63	63
Preferred stock discount accretion and redemptions	1	1
Net income attributable to common shares	1,197	1,165
Less: Dividends and undistributed earnings allocated to participating securities	5	5
Net income attributable to basic common shares	$ 1,192	$ 1,160
Basic weighted-average common shares outstanding (in shares)	455	473
Basic earnings per common share (in dollars per share)	$ 2.62	$ 2.45
Less: Impact of BlackRock earnings per share dilution	$ 3	$ 2
Net income attributable to diluted common shares	$ 1,189	$ 1,158
Dilutive potential common shares (in shares)	1	3
Diluted weighted-average common shares outstanding (in shares)	456	476
Diluted earnings per common share (in dollars per share)	$ 2.61	$ 2.43