Condensed Consolidated Statement of Stockholders' Equity - 9 months ended Jun. 30, 2018 - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balances as of beginning of period at Sep. 30, 2017	$ 449.9	$ 0.2	$ (46.3)	$ 259.0	$ 261.5	$ (24.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	39.8				39.8
Other comprehensive loss	(8.7)					(8.7)
Exercise of stock options	1.8			1.8
Share-based Compensation	4.9			4.9
Balances as of end of period at Jun. 30, 2018	$ 487.7	$ 0.2	$ (46.3)	$ 265.7	$ 301.3	$ (33.2)