Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic earnings per share
Net income	$ 8,380	$ 6,732	$ 25,408	$ 20,209
Less: Preferred stock dividends	379	412	1,167	1,235
Net income applicable to common equity	8,001	6,320	24,241	18,974
Less: Dividends and undistributed earnings allocated to participating securities	53	58	174	188
Net income applicable to common stockholders	$ 7,948	$ 6,262	$ 24,067	$ 18,786
Total weighted-average basic shares outstanding (in shares)	3,376.1	3,534.7	3,416.5	3,570.9
Net income per share (in dollars per share)	$ 2.35	$ 1.77	$ 7.04	$ 5.26
Diluted earnings per share
Net income applicable to common stockholders	$ 7,948	$ 6,262	$ 24,067	$ 18,786
Total weighted-average basic shares outstanding (in shares)	3,376.1	3,534.7	3,416.5	3,570.9
Add: Employee stock options, SARs, warrants and unvested PSUs (in shares)	18.2	24.9	19.7	26.1
Total weighted-average diluted shares outstanding (in shares)	3,394.3	3,559.6	3,436.2	3,597.0
Net income per share (in dollars per share)	$ 2.34	$ 1.76	$ 7.00	$ 5.22