Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (26.7)		$ (24.5)
Other comprehensive loss	(2.2)	$ (0.9)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(23.7)		(21.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2.2)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(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	(26.7)		$ (24.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2.2)
Other comprehensive loss	$ (2.2)