Fair Value Measurements - Foreclosed Assets Remeasured and Reported at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed Assets Remeasured at Initial Recognition Carrying Value Of Foreclosed Assets Prior To Remeasurement	$ 0	$ 1,302
Foreclosed Assets Remeasured at Initial Recognition Charge-offs Recognized in the Allowance for credit losses	0	(76)
Fair Value of Foreclosed Assets Remeasured at Initial Recognition	0	1,226
Foreclosed Assets Remeasured Subsequent to initial Recognition Carrying value of foreclosed assets prior to remeasurement	328	0
Foreclosed Assets Remeasured Subsequent to Initial Recognition Write-downs included in other non-interest expense	(231)	0
Fair Value of Foreclosed Assets remeasured subsequent to initial recognition	$ 97	$ 0