Earnings per Share - EPS Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Numerator:
Net income	$ 69.1	$ 76.6
Less: Allocation to participating securities	(2.4)	(2.4)
Net Income (Loss) from Continuing Operations Available to Common Shareholders, Basic	66.7	74.2
Net income allocated to common stockholders	$ 66.7	$ 74.2
Denominator:
Common shares outstanding (in shares)	30,233,107	29,657,724
Dilutive potential common shares outstanding:
Share-based awards (in shares)	1,041,200	1,092,054
Diluted weighted - average common shares (in shares)	31,274,307	30,749,778