Investment Securities: Narrative-Realized Gains (Losses) (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2023 USD ($) security	Jun. 30, 2022 USD ($) security	Sep. 30, 2022 USD ($)
Schedule of Held-to-maturity and Available-for-sale Securities [Line Items]
Loss on sale of securities	$ 10	$ 2
Held-to-maturity securities, realized loss, number of securities | security	14	16
Asset Pledged as Collateral
Schedule of Held-to-maturity and Available-for-sale Securities [Line Items]
Security owned and pledged as collateral	$ 204,130		$ 133,820