Loans and the Allowance for Credit Losses - Recorded Investment in Non-Accrual Loans (Parenthetical) (Detail) $ in Millions	Sep. 30, 2023 USD ($) Borrower	Dec. 31, 2022 USD ($) Borrower
Receivables [Abstract]
Number of borrowers with loan balance greater than one million | Borrower	3	3
Borrowers with large amount of loans outstanding, minimum amount of loans per borrower	$ 1.0	$ 1.0
Borrowers with large amount of loans outstanding, net	$ 8.3	$ 11.8