v3.20.4
Loans - Summary of estimated fair value of loans and lending commitments (Detail) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Carrying Value $ 116,115 $ 108,904
Loans, Estimated Fair Value 13,625 14,386
Level 2 [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Estimated Fair Value 10,947 12,496
Level 3 [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Estimated Fair Value 2,678 1,890
Amortized cost [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Carrying Value 99,691 89,195
Loans, Estimated Fair Value 101,305 89,186
Amortized cost [Member] | Level 2 [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Estimated Fair Value 52,793 52,091
Amortized cost [Member] | Level 3 [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Estimated Fair Value 48,512 37,095
Held for sale [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Carrying Value 2,799 5,323
Loans Receivable Held-for-sale, Amount 2,799 5,323
Loans, Estimated Fair Value 2,812 5,409
Held for sale [Member] | Level 2 [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Estimated Fair Value 1,541 4,157
Held for sale [Member] | Level 3 [Member]    
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Estimated Fair Value $ 1,271 $ 1,252