Accumulated Other Comprehensive Loss, Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 799.5	$ 614.9	$ 767.5	$ 594.2
Other comprehensive income	(1.6)	(3.4)	12.3	(2.7)
Ending balance	860.2	648.6	860.2	648.6
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(36.0)
Other comprehensive income			12.3
Ending balance	(23.7)		(23.7)
Pension Benefits Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(4.1)
Other comprehensive income			0.0
Ending balance	(4.1)		(4.1)
Accumulated Other Comprehensive Loss, net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(26.2)	(34.8)	(40.1)	(34.8)
Other comprehensive income	(1.6)	(3.4)	12.3	(2.7)
Ending balance	$ (27.8)	$ (38.2)	$ (27.8)	$ (38.2)