Earnings Per Common Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings per common share
Net income	$ 5,777	$ 7,167	$ 20,436	$ 20,869
Preferred stock dividends	(505)	(466)	(1,186)	(1,212)
Net income applicable to common shareholders	$ 5,272	$ 6,701	$ 19,250	$ 19,657
Average common shares issued and outstanding (in shares)	9,303.6	10,031.6	9,516.2	10,177.5
Earnings per common share (in dollars per share)	$ 0.57	$ 0.67	$ 2.02	$ 1.93
Diluted earnings per common share
Net income applicable to common shareholders	$ 5,272	$ 6,701	$ 19,250	$ 19,657
Average common shares issued and outstanding (in shares)	9,303.6	10,031.6	9,516.2	10,177.5
Dilutive potential common shares (in shares)	49.4	139.2	49.5	140.4
Total diluted average common shares issued and outstanding (in shares)	9,353.0	10,170.8	9,565.7	10,317.9
Diluted earnings per common share (in dollars per share)	$ 0.56	$ 0.66	$ 2.01	$ 1.91