v3.21.2
Regulation and Capital Adequacy - Changes in Risk-weighted Assets (Detail) - USD ($)
$ in Millions
 9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Standardized Capital Rules [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Risk-Weighted Assets, Beginning balance $ 554,162 $ 563,575
Change in Credit RWAs 97,192 (13,549)
Change in Market RWAs 12,582 4,136
Risk-Weighted Assets, end of period 663,936 554,162
Standardized Capital Rules [Member] | Derivatives [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 27,298 (614)
Standardized Capital Rules [Member] | Commitments Guarantees and Loans [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 46,477 (3,239)
Standardized Capital Rules [Member] | Securities Financing Transactions [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 16,964 5,560
Standardized Capital Rules [Member] | Equity Investments [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 2,402 (9,870)
Standardized Capital Rules [Member] | Other [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 4,051 (5,386)
Standardized Capital Rules [Member] | Regulatory VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs (2,180) 5,980
Standardized Capital Rules [Member] | Stressed VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 8,944 1,067
Standardized Capital Rules [Member] | Incremental Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 443 3,574
Standardized Capital Rules [Member] | Comprehensive Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 1,534 365
Standardized Capital Rules [Member] | Specific Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 3,841 (6,850)
Advanced Capital Rules [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Risk-Weighted Assets, Beginning balance 609,750 544,653
Change in Credit RWAs 46,979 51,634
Change in Market RWAs 12,582 4,338
Change in operational risk 2,750 9,125
Risk-Weighted Assets, end of period 672,061 609,750
Advanced Capital Rules [Member] | Derivatives [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 5,280 39,060
Advanced Capital Rules [Member] | Commitments Guarantees and Loans [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 26,499 17,131
Advanced Capital Rules [Member] | Securities Financing Transactions [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 1,436 2,734
Advanced Capital Rules [Member] | Equity Investments [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 6,182 (12,624)
Advanced Capital Rules [Member] | Other [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 7,582 5,333
Advanced Capital Rules [Member] | Regulatory VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs (2,180) 5,980
Advanced Capital Rules [Member] | Stressed VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 8,944 1,067
Advanced Capital Rules [Member] | Incremental Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 443 3,574
Advanced Capital Rules [Member] | Comprehensive Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 1,534 567
Advanced Capital Rules [Member] | Specific Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs $ 3,841 $ (6,850)