v3.20.4
Loans - Summary of Financing receivable, past due (Detail) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due $ 804 $ 627
Past due loans divided by gross loans at amortized cost 0.80% 0.70%
Corporate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due $ 294 $ 239
Wealth management [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 92 28
Commercial real estate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 232 177
Residential real estate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 27 37
Installment [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 58 100
Credit Card Receivable [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 77 39
Other [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 24 7
30-89 days [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 219 395
30-89 days [Member] | Corporate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due   197
30-89 days [Member] | Wealth management [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 58 13
30-89 days [Member] | Commercial real estate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 49 54
30-89 days [Member] | Residential real estate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 4 19
30-89 days [Member] | Installment [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 42 71
30-89 days [Member] | Credit Card Receivable [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 46 35
30-89 days [Member] | Other [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 20 6
90 days or more [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 585 232
90 days or more [Member] | Corporate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 294 42
90 days or more [Member] | Wealth management [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 34 15
90 days or more [Member] | Commercial real estate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 183 123
90 days or more [Member] | Residential real estate [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 23 18
90 days or more [Member] | Installment [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 16 29
90 days or more [Member] | Credit Card Receivable [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due 31 4
90 days or more [Member] | Other [Member]    
Financing Receivable, Past Due [Line Items]    
Financing receivable, past due $ 4 $ 1