Loans and Allowance for Credit Losses - Summary of Gross Charge Offs (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2026	Sep. 30, 2025	Mar. 31, 2025
Financing Receivable, Past Due [Line Items]
2026	$ 0		$ 0
2025	4,084		3,551
2024	6,533		5,210
2023	5,829		5,769
2022	4,926		2,361
Prior	5,508		7,755
Total	26,880		24,646
Recreation [Member]
Financing Receivable, Past Due [Line Items]
2026	0		0
2025	3,685		2,728
2024	5,617		3,707
2023	4,501		4,506
2022	3,974		1,933
Prior	4,714		7,400
Total	22,491		20,274
Home Improvement [Member]
Financing Receivable, Past Due [Line Items]
2026	0		0
2025	399		823
2024	916		1,503
2023	1,328		1,133
2022	952		428
Prior	756		340
Total	4,351		4,227
Commercial Loan [Member]
Financing Receivable, Past Due [Line Items]
2026	0		0
2025	0		0
2024	0		0
2023	0		130
2022	0		0
Prior	0		0
Total	0		130
Taxi Medallion [Member]
Financing Receivable, Past Due [Line Items]
2026	0	$ 0
2025	0		0
2024	0		0
2023	0		0
2022	0		0
Prior	38		15
Total	$ 38		$ 15

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Amount, excluding accrued interest, of writeoff of financing receivable originated more than five years before current fiscal year. Excludes net investment in lease.

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