v3.21.2
Other Assets - Other Assets (Parenthetical) (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Schedule Of Other Assets [Line Items]          
Accumulated depreciation and amortization $ 10,730   $ 10,730   $ 10,120
Property, leasehold improvements and equipment used for operation 6,550   6,550   6,540
Foreclosed real estate included in property, leasehold improvements and equipment $ 218   $ 218   $ 318
Amortization period - Capitalized costs of software developed or obtained for internal use 3 years   3 years   3 years
Operating lease right-of-use assets $ 2,288   $ 2,288   $ 2,280
Investments in qualified affordable housing projects 681   681   678
Property Leasehold Improvements And Equipment [Member]          
Schedule Of Other Assets [Line Items]          
Impairment of property leasehold improvements and equipment 0 $ 0 134 $ 132  
Asset Management [Member]          
Schedule Of Other Assets [Line Items]          
Assets classified as held for sale 3,660   3,660   $ 437
European headquarters in London [Member]          
Schedule Of Other Assets [Line Items]          
Operating lease right-of-use assets $ 230 $ 152 $ 230 $ 152