Federal Income Taxes: Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Federal									$ 7,167	$ 6,139	$ 6,570
Deferred									(291)	(177)	275
Provision for income taxes	$ 1,624	$ 1,666	$ 1,705	$ 1,881	$ 1,785	$ 1,472	$ 1,316	$ 1,389	$ 6,876	$ 5,962	$ 6,845