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, 2020	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net (loss) income		$ (41.6)	$ 44.4	$ (15.1)
Weighted average number of common shares outstanding – basic		103,670,000	102,800,000	83,369,000
Basic (loss) earnings per share		$ (0.40)	$ 0.43	$ (0.18)
Weighted average number of common shares outstanding – diluted		103,670,000	103,363,000	83,369,000
Diluted (loss) earnings per share		$ (0.40)	$ 0.43	$ (0.18)
Weighted average number of anti-dilutive options and restricted stock	[1]	8,210,000	5,935,000	1,283,000

[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.