Stock Compensation Plans: Stock Options by Exercise Price (Details) - Stock Options	12 Months Ended
	Sep. 30, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding, Number (in shares) | shares	369,150
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 24.00
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	6 years
Options Exercisable, Number (in shares) | shares	239,030
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 23.03
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	4 years 10 months 24 days
9.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 9
Options Outstanding, Number (in shares) | shares	3,000
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 9.00
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 month 6 days
Options Exercisable, Number (in shares) | shares	3,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 9.00
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	1 month 6 days
10.26 - 10.71
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 10.26
Exercise price range, upper range limit (in dollars per share)	$ 10.71
Options Outstanding, Number (in shares) | shares	43,250
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 10.55
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 year 4 months 24 days
Options Exercisable, Number (in shares) | shares	43,250
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 10.55
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	1 year 4 months 24 days
15.67 - 19.13
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 15.67
Exercise price range, upper range limit (in dollars per share)	$ 19.13
Options Outstanding, Number (in shares) | shares	70,770
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 16.54
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	5 years 9 months 18 days
Options Exercisable, Number (in shares) | shares	47,110
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 16.34
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	5 years 2 months 12 days
26.50 - 27.14
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 26.5
Exercise price range, upper range limit (in dollars per share)	$ 27.40
Options Outstanding, Number (in shares) | shares	106,660
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 27.32
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	8 years
Options Exercisable, Number (in shares) | shares	42,600
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 27.23
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	7 years 1 month 6 days
28.23 - 29.69
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 28.23
Exercise price range, upper range limit (in dollars per share)	$ 29.69
Options Outstanding, Number (in shares) | shares	110,750
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 28.78
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	6 years 6 months
Options Exercisable, Number (in shares) | shares	69,350
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 29.11
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	5 years 7 months 6 days
31.80
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 31.8
Options Outstanding, Number (in shares) | shares	34,720
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 31.85
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	5 years 1 month 6 days
Options Exercisable, Number (in shares) | shares	33,720
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 31.80
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	5 years