Loans and Allowance for Loan Losses (Additional Information) (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Impaired, Commitment to Lend	$ 1,000		$ 1,000
Impaired Financing Receivable, Unpaid Principal Balance	14,160,000		14,095,000
Mortgage Loans in Process of Foreclosure, Amount	1,200,000		1,300,000
Troubled Debt Restructuring, Debtor, Subsequent Periods, Contingent Payments, Amount	114,000
Servicing Assets Valuation Allowance	177,000		177,000
Loan Servicing Rights [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	131,800,000	$ 77,700,000	120,600,000
Financial Service Revenue	272,000	150,000
Loan Servicing Rights [Member] | Bank Servicing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 7,000	$ 2,000
Troubled Debt Restructuring [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance, Covered			$ 5,000