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	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net (loss) income	$ (2.4)	$ 31.7	$ (35.5)	$ 19.3
Weighted average number of common shares outstanding – basic	103,793,000	102,828,000	103,583,000	102,705,000
Basic (loss) earnings per share	$ (0.02)	$ 0.31	$ (0.34)	$ 0.19
Weighted average number of common shares outstanding – diluted	103,793,000	102,999,000	103,583,000	103,300,000
Diluted (loss) earnings per share	$ (0.02)	$ 0.31	$ (0.34)	$ 0.19
Weighted average number of anti-dilutive options and restricted stock	8,760,000	6,356,000	8,285,000	6,406,000