Accumulated Other Comprehensive Loss, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 860.2	$ 648.6	$ 767.5	$ 594.2
Other comprehensive income	4.0	0.0	16.3	(2.7)
Ending balance	901.4	688.8	901.4	688.8
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(36.0)
Other comprehensive income			16.3
Ending balance	(19.7)		(19.7)
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	(27.8)	(38.2)	(40.1)	(34.8)
Other comprehensive income	4.0		16.3	(2.7)
Ending balance	$ (23.8)	$ (38.2)	$ (23.8)	$ (38.2)