Share-Based Compensation - Restricted Stock Plan Table (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Shares Available for Grant
Shares Available for Grant, Beginning (in shares)	861,454
Shares Available for Grant, Granted	307,204
Shares Available for Grant, Forfeited	4,048
Shares Available for Grant, Ending (in shares)	558,298	861,454
Number of Shares Outstanding
Number of Shares Outstanding, Beginning (in shares)	484,346
Number of Shares Outstanding, Granted	307,204
Number of Shares Outstanding, Vested (in shares)	(210,461)
Number of Shares Outstanding, Forfeited (in shares)	(4,048)
Number of Shares Outstanding, Ending (in shares)	577,041	484,346
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning (in dollar per share)	$ 42.97
Weighted Average Grant Date Fair Value, Granted (in dollar per share)	57.33
Weighted Average Grant Date Fair Value, Vested (in dollar per share)	43.11
Weighted Average Grant Date Fair Value, Forfeited (in dollar per share)	41.81
Weighted Average Grant Date Fair Value, Ending (in dollars per share)	$ 50.57	$ 42.97
Stock Option Activity, Additional Disclosures
Weighted Average Remaining Term (in years)	1 year 3 months 3 days	1 year 4 months 13 days
Aggregate Intrinsic Value	$ 38.0	$ 24.8