Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (loss) by Component, Net of Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Changes in Other Comprehensive Income by Component, Net of Tax [Roll Forward]
Balance	$ 122,529	$ 78,043
Net current period other comprehensive income (loss)	(876)	100
Balance	172,584	122,529
Accumulated Other Comprehensive Income [Member]
Changes in Other Comprehensive Income by Component, Net of Tax [Roll Forward]
Balance	256	156
Net current period other comprehensive income (loss)	(876)	100
Balance	(620)	256
Unrealized Gains and Losses on Available-for-Sale Debt Securities
Changes in Other Comprehensive Income by Component, Net of Tax [Roll Forward]
Balance	256	156
Other comprehensive income (loss)	(795)	291
Amount reclassified from accumulated other comprehensive income	(81)	(191)
Net current period other comprehensive income (loss)	876	100
Balance	$ (620)	$ 256