Loans and Allowance for Loan Losses (Troubled Debt Restructurings) (Detail) $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($) Number
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans | Number	3
Pre-Modification Principal Balance	$ 1,847
Post-Modification Principal Balance	$ 1,847
Commercial real estate [Member]
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans | Number	1
Pre-Modification Principal Balance	$ 1,674
Post-Modification Principal Balance	$ 1,674
Commercial Business [Member]
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans | Number	1
Pre-Modification Principal Balance	$ 170
Post-Modification Principal Balance	$ 170
Consumer [Member]
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans | Number	1
Pre-Modification Principal Balance	$ 3
Post-Modification Principal Balance	$ 3