Share-Based Compensation - Restricted Stock Plan Table (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Shares Available for Grant
Shares available for grant, beginning (in shares)	558,298
Shares available for grant, granted (in shares)	(269,129)
Shares available for grant, forfeited (in shares)	642
Shares available for grant, ending (in shares)	289,811	558,298
Number of Shares Outstanding
Number of shares outstanding, beginning (in shares)	577,041
Number of shares outstanding, granted (in shares)	269,129
Number of shares outstanding, vested (in shares)	(265,862)
Number of shares outstanding, forfeited (in shares)	(642)
Number of shares outstanding, ending (in shares)	579,666	577,041
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning (in dollar per share)	$ 50.57
Weighted average grant date fair value, granted (in dollar per share)	69.41
Weighted average grant date fair value, vested (in dollar per share)	48.60
Weighted average grant date fair value, forfeited (in dollar per share)	53.44
Weighted average grant date fair value, ending (in dollars per share)	$ 60.22	$ 50.57
Stock Option Activity, Additional Disclosures
Weighted average remaining term (in years)	1 year 2 months 19 days	1 year 3 months 3 days
Aggregate intrinsic value	$ 48.1	$ 38.0