Investment Securities: Narrative-Realized Gains (Losses) (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($) security	Sep. 30, 2021 USD ($) security
Schedule of Held-to-maturity and Available-for-sale Securities [Line Items]
Loss on sale of securities	$ 11	$ 1	$ 12
Held-to-maturity securities, realized loss, number of securities | security		16	19
Asset Pledged as Collateral
Schedule of Held-to-maturity and Available-for-sale Securities [Line Items]
Security owned and pledged as collateral	$ 201,817	$ 133,824