Loans Receivable - Classes of Loan Portfolio Summarized by Aging Categories (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	$ 1,444,734	$ 1,350,471
31-60 Days Past Due, Accruing Loans	7,111	1,514
61-90 Days Past Due, Accruing Loans	984	585
Greater than 90 Days Past Due, Accruing Loans	1,482	5,519
Total Past Due, Accruing Loans	9,577	7,618
Purchased Credit Impaired, Accruing Loans		877
Total Accruing Loans	1,454,311	1,358,966
Non-Accrual Loans	15,082	15,867
Obligations of States and Political Subdivisions [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	40,416	56,164
Total Accruing Loans	40,416	56,164
Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	42,842	38,223
31-60 Days Past Due, Accruing Loans	121	44
61-90 Days Past Due, Accruing Loans	144
Greater than 90 Days Past Due, Accruing Loans	63	159
Total Past Due, Accruing Loans	328	203
Total Accruing Loans	43,170	38,426
Non-Accrual Loans	338	463
Auto Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	3,462	13,576
31-60 Days Past Due, Accruing Loans	134	271
61-90 Days Past Due, Accruing Loans	2	5
Greater than 90 Days Past Due, Accruing Loans	13
Total Past Due, Accruing Loans	149	276
Total Accruing Loans	3,611	13,852
Non-Accrual Loans	21	43
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	1,685	1,513
31-60 Days Past Due, Accruing Loans		59
61-90 Days Past Due, Accruing Loans	31
Greater than 90 Days Past Due, Accruing Loans		9
Total Past Due, Accruing Loans	31	68
Total Accruing Loans	1,716	1,581
Non-Accrual Loans	6	14
Residential [Member] | Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	621,270	576,960
31-60 Days Past Due, Accruing Loans	598	1,029
61-90 Days Past Due, Accruing Loans	367	580
Greater than 90 Days Past Due, Accruing Loans	1,140	1,744
Total Past Due, Accruing Loans	2,105	3,353
Total Accruing Loans	623,375	580,313
Non-Accrual Loans	1,594	2,865
Construction [Member] | Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	25,024	14,013
Total Accruing Loans	25,024	14,013
Commercial [Member] | Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	672,875	587,779
31-60 Days Past Due, Accruing Loans	5,719	111
Greater than 90 Days Past Due, Accruing Loans	247	2,350
Total Past Due, Accruing Loans	5,966	2,461
Purchased Credit Impaired, Accruing Loans		877
Total Accruing Loans	678,841	591,117
Non-Accrual Loans	12,165	11,124
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current, Accruing Loans	37,160	62,243
31-60 Days Past Due, Accruing Loans	539
61-90 Days Past Due, Accruing Loans	440
Greater than 90 Days Past Due, Accruing Loans	19	1,257
Total Past Due, Accruing Loans	998	1,257
Total Accruing Loans	38,158	63,500
Non-Accrual Loans	$ 958	$ 1,358