Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023		Jun. 30, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period		$ 227,661	$ 212,269	$ 218,569	[1]	$ 206,899
Balance at end of period		229,263	214,319	229,263		214,319
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	[2]	(495)	(107)	(717)		59
Other comprehensive loss	[2]	(249)	(458)	(27)		(624)
Balance at end of period	[2]	(744)	(565)	(744)		(565)
Accumulated Net Unrealized Investment Gain (Loss) | Available-for-sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	[2]	(486)	(95)	(706)		75
Other comprehensive loss	[2]	(249)	(459)	(29)		(629)
Balance at end of period	[2]	(735)	(554)	(735)		(554)
Accumulated Net Unrealized Investment Gain (Loss) | Held-to-maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	[2]	(9)	(12)	(11)		(16)
Other comprehensive loss	[2]	0	1	2		5
Balance at end of period	[2]	$ (9)	$ (11)	$ (9)		$ (11)

[1] Derived from audited consolidated financial statements.

[2] All amounts are net of income taxes.