Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (38.2)		$ (38.2)		$ (34.8)
ASU 2018-02 cumulative transition adjustment					0.7
Other comprehensive (loss) income	(3.4)	$ 0.0	(2.7)	$ 0.3
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(34.2)		(34.2)		(31.5)
ASU 2018-02 cumulative transition adjustment					0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(2.7)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(4.0)		(4.0)		(3.3)
ASU 2018-02 cumulative transition adjustment					(0.7)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0.0
Accumulated Other Comprehensive Loss, net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(38.2)		(38.2)		(34.8)
ASU 2018-02 cumulative transition adjustment					$ (0.7)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(2.7)
Other comprehensive (loss) income	$ (3.4)		$ (2.7)	$ 0.3