Accumulated Other Comprehensive Loss, Net (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 953.0	$ 904.0	$ 799.5	$ 904.0	$ 767.5
Other comprehensive income/(loss), net of tax	(16.9)	(1.4)	(1.6)	(18.3)	12.3
Ending balance	1,005.6	953.0	860.2	1,005.6	860.2
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(24.0)	(22.7)		(22.7)
Other comprehensive income/(loss), net of tax	1.2	(1.3)
Ending balance	(22.8)	(24.0)		(22.8)
Pension Benefits Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2.4)	(2.4)		(2.4)
Other comprehensive income/(loss), net of tax	0.0	0.0
Ending balance	(2.4)	(2.4)		(2.4)
Cash Flow Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(0.1)	0.0		0.0
Other comprehensive income/(loss), net of tax	(18.1)	(0.1)
Ending balance	(18.2)	(0.1)		(18.2)
Accumulated Other Comprehensive Loss, net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(26.5)	(25.1)	(26.2)	(25.1)	(40.1)
Other comprehensive income/(loss), net of tax	(16.9)		(1.6)	(18.3)	12.3
Ending balance	$ (43.4)	$ (26.5)	$ (27.8)	$ (43.4)	$ (27.8)