Accumulated Other Comprehensive Loss, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 767.5	$ 594.2
Other comprehensive income	13.9	0.7
Ending balance	799.5	614.9
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(36.0)
Other comprehensive income	13.9
Ending balance	(22.1)
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)
Accumulated Other Comprehensive Loss, net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(40.1)	(34.8)
Other comprehensive income	13.9	0.7
Ending balance	$ (26.2)	$ (34.8)