v3.21.2
Loans - Summary of Credit Concentration by Region (Detail) - USD ($)
$ in Millions
9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 146,956 $ 119,989
Concentration Risk,Percentage 100.00% 100.00%
Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 75.00% 75.00%
Europe, Middle East and Africa [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 20.00% 19.00%
Asia [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 5.00% 6.00%
Corporate [Member]    
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 54,107 $ 48,659
Concentration Risk,Percentage 100.00% 100.00%
Corporate [Member] | Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 56.00% 60.00%
Corporate [Member] | Europe, Middle East and Africa [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 36.00% 31.00%
Corporate [Member] | Asia [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 8.00% 9.00%
Wealth management [Member]    
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 41,775 $ 33,023
Concentration Risk,Percentage 100.00% 100.00%
Wealth management [Member] | Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 86.00% 88.00%
Wealth management [Member] | Europe, Middle East and Africa [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 11.00% 10.00%
Wealth management [Member] | Asia [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 3.00% 2.00%
Commercial real estate [Member]    
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 21,707 $ 20,290
Concentration Risk,Percentage 100.00% 100.00%
Commercial real estate [Member] | Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 75.00% 71.00%
Commercial real estate [Member] | Europe, Middle East and Africa [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 19.00% 19.00%
Commercial real estate [Member] | Asia [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 6.00% 10.00%
Residential real estate [Member]    
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 13,359 $ 5,750
Concentration Risk,Percentage 100.00% 100.00%
Residential real estate [Member] | Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 92.00% 88.00%
Residential real estate [Member] | Europe, Middle East and Africa [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 5.00% 9.00%
Residential real estate [Member] | Asia [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 3.00% 3.00%
Installment [Member]    
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 3,449 $ 3,823
Concentration Risk,Percentage 100.00% 100.00%
Installment [Member] | Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 100.00% 100.00%
Credit card [Member]    
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 6,251 $ 4,270
Concentration Risk,Percentage 100.00% 100.00%
Credit card [Member] | Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 100.00% 100.00%
Other [Member]    
Product Information [Line Items]    
Loans and Leases Receivable, Gross $ 6,308 $ 4,174
Concentration Risk,Percentage 100.00% 100.00%
Other [Member] | Americas [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 88.00% 81.00%
Other [Member] | Europe, Middle East and Africa [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 10.00% 17.00%
Other [Member] | Asia [Member]    
Product Information [Line Items]    
Concentration Risk,Percentage 2.00% 2.00%