Stock Compensation Plans: Stock Option Activity (Details) - $ / shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Number of Shares
Options outstanding, beginning of period (in shares)	421,925	406,815	395,349
Options granted (in shares)	1,000	74,000	81,000
Options exercised (in shares)	(42,635)	(36,720)	(64,264)
Options forfeited (in shares)	(11,140)	(22,170)	(5,270)
Options outstanding, end of period (in shares)	369,150	421,925	406,815
Weighted Average Exercise Price
Options outstanding, beginning of period (in dollars per share)	$ 23.30	$ 21.62	$ 18.45
Options granted (in dollars per share)	33.40	27.40	28.06
Options exercised (in dollars per share)	16.38	11.31	9.81
Options forfeited (in dollars per share)	27.26	26.01	26.91
Options outstanding, end of period (in dollars per share)	$ 24.00	$ 23.30	$ 21.62