Loans - Summary of Estimated Fair Value of Loans and Lending Commitments that are not Accounted for at Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]
Loans	$ 178,257	$ 179,286
Amortized Cost
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]
Loans	162,319	167,037
Loans, Estimated Fair Value, Total	163,417	169,042
Amortized Cost | Level 2
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]
Loans, Estimated Fair Value, Level 2	88,954	85,921
Amortized Cost | Level 3
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]
Loans, Estimated Fair Value, Level 3	74,463	83,121
Held For Sale
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]
Loans	9,490	4,594
Loans held for sale	9,490	4,594
Loans held for sale, Estimated Fair Value, Total	9,500	4,606
Held For Sale | Level 2
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]
Loans held for sale, Estimated Fair Value, Level 2	7,815	2,592
Held For Sale | Level 3
Schedule Of Estimated Fair Value Of Loans And Lending Commitments That Are Not Accounted For At Fair Value [Line Items]
Loans held for sale, Estimated Fair Value, Level 3	$ 1,685	$ 2,014