Net Income Per Common Share: Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, $ 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
Earnings Per Share, Basic [Abstract]
Net income to common shareholders									$ 27,118	$ 23,600	$ 27,583
Denominator – weighted average common shares outstanding (shares)									8,175,898	8,304,002	8,340,983
Basic net income per common share (in dollars per share)	$ 0.82	$ 0.77	$ 0.81	$ 0.91	$ 0.86	$ 0.69	$ 0.64	$ 0.66	$ 3.32	$ 2.84	$ 3.31
Diluted net income per common share computation
Effect of dilutive stock options (shares)									72,283	79,333	103,350
Weighted average common shares outstanding-assuming dilution (shares)									8,248,181	8,383,335	8,444,333
Diluted net income per common share (in dollars per share)	$ 0.81	$ 0.77	$ 0.80	$ 0.90	$ 0.85	$ 0.69	$ 0.63	$ 0.65	$ 3.29	$ 2.82	$ 3.27