Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (24.8)		$ (24.8)		$ (24.6)
Other comprehensive loss	0.7	$ (1.3)	(0.2)	$ (6.7)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(20.3)		(20.3)		(20.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(0.2)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(4.5)		(4.5)		(4.5)
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	$ (24.8)		(24.8)		$ (24.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(0.2)
Other comprehensive loss			$ (0.2)