Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share, Diluted, by Common Class, Including Two Class Method
Net earnings available to common stockholders, basic	$ 82.3	$ 27.6	$ 23.5
Dilutive securities, effect on basic earnings per share	0.0	0.2	0.1
Net earnings available to common stockholders, diluted	$ 82.3	$ 27.8	$ 23.6
Weighted-Average common shares outstanding, basic (in shares)	93.5	39.5	39.4
Weighted-Average common shares outstanding, diluted (in shares)	93.8	39.7	39.5
Earnings per common share, basic (in usd per share)	$ 0.88	$ 0.70	$ 0.60
Earnings per common share, diluted (in usd per share)	$ 0.88	$ 0.70	$ 0.60
Antidilutive securities excluded from computation of earnings per share, amount	0.2	0.2	0.1
Restricted Stock Units (RSUs)
Earnings Per Share, Diluted, by Common Class, Including Two Class Method
Weighted-Average common shares outstanding, diluted (in shares)	0.2	0.2	0.1
Performance-based restricted stock units (PRSUs)
Earnings Per Share, Diluted, by Common Class, Including Two Class Method
Weighted-Average common shares outstanding, diluted (in shares)	0.1	0.0	0.0