Business Segments - Assets by Segment (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total	$ 1,132,059	$ 1,141,523	$ 992,968
Investment Banking [Member]
Segment Reporting Information [Line Items]
Total	118,309		92,009
Global Markets [Member]
Segment Reporting Information [Line Items]
Total	818,255		725,060
Asset Management [Member]
Segment Reporting Information [Line Items]
Total	94,897		92,102
Consumer & Wealth Management [Member]
Segment Reporting Information [Line Items]
Total	$ 100,598		$ 83,797