Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 1,126	$ 1,006	$ 3,297	$ 2,938
Net income attributable to noncontrolling interests	12	18	39	60
Preferred stock dividends	63	63	181	168
Preferred stock discount accretion and redemptions	1	1	24	4
Net income attributable to common shares	1,050	924	3,053	2,706
Dividends and undistributed earnings allocated to participating securities	5	7	15	19
Net income attributable to basic common shares	$ 1,045	$ 917	$ 3,038	$ 2,687
Basic weighted-average common shares outstanding	479	490	483	496
Basic earnings per common share	$ 2.18	$ 1.87	$ 6.29	$ 5.41
Less: Impact of BlackRock earnings per share dilution	$ 3	$ 4	$ 8	$ 10
Net income attributable to diluted common shares	$ 1,042	$ 913	$ 3,030	$ 2,677
Dilutive potential common shares	4	6	5	6
Diluted weighted-average common shares outstanding	483	496	488	502
Diluted earnings per common share	$ 2.16	$ 1.84	$ 6.21	$ 5.33