v3.21.2
Loans - Summary of estimated fair value of loans and lending commitments (Detail) - USD ($)
$ in Millions
Sep. 30, 2021
Dec. 31, 2020
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]    
Loans, Carrying Value $ 143,624 $ 116,115
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 126,026 99,691
Loans, Estimated Fair Value 127,163 101,305
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 71,984 52,793
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 55,179 48,512
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 5,494 2,799
Loans Receivable Held-for-sale, Amount 5,494 2,799
Loans, Estimated Fair Value 5,516 2,812
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 2,898 1,541
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 $ 2,618 $ 1,271