Earnings (Loss) Per Share of Common Stock - Reconciliation of Numerator and Denominator for Basic and Diluted Earnings (loss) Per Share Calculation (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net (loss) income available to common stockholders		$ 46.3	$ (41.6)	$ 44.4
Weighted average number of common shares outstanding – basic		105,183,000	103,670,000	102,800,000
Basic (loss) earnings per share		$ 0.44	$ (0.40)	$ 0.43
Weighted average number of common shares outstanding – diluted		105,690,000	103,670,000	103,363,000
Diluted (loss) earnings per share		$ 0.44	$ (0.40)	$ 0.43
Weighted average number of anti-dilutive options and restricted stock	[1]	7,452,000	8,210,000	5,935,000

[1] Weighted average number of anti-dilutive options is based upon the average closing price of the Company’s common stock on the NYSE for the period.