Earnings Per Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 39.9	$ 112.5	$ 222.2	$ 264.5
Less: Distributed and undistributed income available to participating securities, Basic	(0.1)	(0.1)	(0.1)	(0.1)
Distributed and undistributed income available to common stockholders, Basic	39.8	112.4	222.1	264.4
Less: Distributed and undistributed income available to participating securities, Diluted	(0.1)	(0.1)	(0.1)	(0.1)
Distributed and undistributed (loss) income available to common stockholders, Diluted	$ 39.8	$ 112.4	$ 222.1	$ 264.4
Basic weighted average shares outstanding	263.4	264.9	264.0	263.8
Effect of dilutive stock options and non- participating securities	1.9	2.1	2.1	2.1
Diluted weighted average shares outstanding	265.3	267.0	266.1	265.9
Basic earnings per share attributable to common stockholders	$ 0.15	$ 0.42	$ 0.84	$ 1.00
Diluted earnings per share attributable to common stockholders	$ 0.15	$ 0.42	$ 0.83	$ 0.99