Other Assets - Goodwill and Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	$ 4,326	$ 4,332
Identifiable Intangible Assets	497	630
Investment Banking [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	281	281
Global Markets - Fixed Income, Currency and Commodities [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	269	269
Identifiable Intangible Assets	1	2
Global Markets - Equities [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	2,638	2,644
Identifiable Intangible Assets	43	45
Asset Management [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	390	390
Identifiable Intangible Assets	180	274
Consumer banking [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	48	48
Identifiable Intangible Assets		6
Wealth management [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	700	700
Identifiable Intangible Assets	$ 273	$ 303