Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (33.2)		$ (33.2)		$ (24.5)
Other comprehensive loss	(4.9)	$ (1.9)	(8.7)	$ (2.1)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(30.2)		(30.2)		(21.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(8.7)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(3.0)		(3.0)		(3.0)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0.0
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (33.2)		(33.2)		$ (24.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(8.7)
Other comprehensive loss			$ (8.7)