Fair Value Measurements - Foreclosed Assets Remeasured and Reported at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
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	$ 2,898	$ 0
Foreclosed Assets Remeasured at Initial Recognition Charge-offs recognized in the allowance for loan losses	0	0
Fair Value of Foreclosed Assets Remeasured at Initial Recognition	2,898	0
Foreclosed Assets Remeasured Subsequent to initial Recognition Carrying value of foreclosed assets prior to remeasurement	1,823	89
Foreclosed Assets Remeasured Subsequent to Initial Recognition Write-downs included in other non-interest expense	(473)	(16)
Fair Value of Foreclosed Assets remeasured subsequent to initial recognition	$ 1,350	$ 73