Fair Value Measurements - Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	$ 20,051	$ 7,999
Impaired Financing Receivable, Related Allowance	(1,452)	(1,742)
Loans receivable, fair value disclosure	18,599	6,257
Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	24,921	2,087
Impaired Financing Receivable, Related Allowance	(4,849)
Impaired Financing Receivable, Reversal of Specific Valuation Allowance Allocations		4,881
Loans receivable, fair value disclosure	$ 20,072	$ 6,968