v3.20.4
Regulation and Capital Adequacy - Changes in Risk-weighted Assets (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Standardized Capital Rules [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Risk-Weighted Assets, Beginning balance $ 563,575 $ 547,910
Change in Credit RWAs (13,549) 25,649
Change in Market RWAs 4,136 (9,984)
Risk-Weighted Assets, end of period 554,162 563,575
Standardized Capital Rules [Member] | Derivatives [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs (614) (1,605)
Standardized Capital Rules [Member] | Commitments Guarantees and Loans [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs (3,239) 19,435
Standardized Capital Rules [Member] | Securities Financing Transactions [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 5,560 (496)
Standardized Capital Rules [Member] | Equity Investments [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs (9,870) 3,251
Standardized Capital Rules [Member] | Other [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs (5,386) 5,064
Standardized Capital Rules [Member] | Regulatory VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 5,980 1,151
Standardized Capital Rules [Member] | Stressed VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 1,067 2,959
Standardized Capital Rules [Member] | Incremental Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 3,574 (6,161)
Standardized Capital Rules [Member] | Comprehensive Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 365 (1,377)
Standardized Capital Rules [Member] | Specific Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs (6,850) (6,556)
Advanced Capital Rules [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Risk-Weighted Assets, Beginning balance 544,653 558,111
Change in Credit RWAs 51,634 (7,672)
Change in Market RWAs 4,338 (10,186)
Change in operational risk 9,125 4,400
Risk-Weighted Assets, end of period 609,750 544,653
Advanced Capital Rules [Member] | Derivatives [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 39,060 (9,670)
Advanced Capital Rules [Member] | Commitments Guarantees and Loans [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 17,131 (8,900)
Advanced Capital Rules [Member] | Securities Financing Transactions [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 2,734 (4,425)
Advanced Capital Rules [Member] | Equity Investments [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs (12,624) 6,738
Advanced Capital Rules [Member] | Other [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 5,333 8,585
Advanced Capital Rules [Member] | Regulatory VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 5,980 1,151
Advanced Capital Rules [Member] | Stressed VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 1,067 2,959
Advanced Capital Rules [Member] | Incremental Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 3,574 (6,161)
Advanced Capital Rules [Member] | Comprehensive Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 567 (1,579)
Advanced Capital Rules [Member] | Specific Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs $ (6,850) $ (6,556)