v3.20.4
Regulation and Capital Adequacy - Risk-weighted Assets (Detail) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Standardized [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs $ 485,438 $ 498,987  
Market RWAs 68,724 64,588  
Total RWAs 554,162 563,575 $ 547,910
Standardized [Member] | Derivatives [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 120,292 120,906  
Standardized [Member] | Commitments Guarantees and Loans [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 176,501 179,740  
Standardized [Member] | Securities Financing Transactions [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 71,427 65,867  
Standardized [Member] | Equity Investments [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 46,944 56,814  
Standardized [Member] | Other [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 70,274 75,660  
Standardized [Member] | Regulatory VaR [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 14,913 8,933  
Standardized [Member] | Stressed VaR [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 31,978 30,911  
Standardized [Member] | Incremental Risk [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 7,882 4,308  
Standardized [Member] | Comprehensive Risk [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 1,758 1,393  
Standardized [Member] | Specific Risk [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 12,193 19,043  
Advanced [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 412,713 361,079  
Market RWAs 68,724 64,386  
Total Operational RWAs 128,313 119,188  
Total RWAs 609,750 544,653 $ 558,111
Advanced [Member] | Derivatives [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 111,691 72,631  
Advanced [Member] | Commitments Guarantees and Loans [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 151,587 134,456  
Advanced [Member] | Securities Financing Transactions [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 16,568 13,834  
Advanced [Member] | Equity Investments [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 49,268 61,892  
Advanced [Member] | Other [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Credit RWAs 83,599 78,266  
Advanced [Member] | Regulatory VaR [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 14,913 8,933  
Advanced [Member] | Stressed VaR [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 31,978 30,911  
Advanced [Member] | Incremental Risk [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 7,882 4,308  
Advanced [Member] | Comprehensive Risk [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs 1,758 1,191  
Advanced [Member] | Specific Risk [Member]      
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]      
Market RWAs $ 12,193 $ 19,043