Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (34.8)		$ (34.8)
ASU 2018-02 cumulative transition adjustment			0.7
Other comprehensive income	0.7	$ 0.3
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(30.8)		(31.5)
ASU 2018-02 cumulative transition adjustment			0.0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0.7
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(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	(34.8)		(34.8)
ASU 2018-02 cumulative transition adjustment			$ (0.7)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0.7
Other comprehensive income	$ 0.7	$ 0.3