Consolidated Statements of Shareholders’ Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balances at beginning of period at Sep. 30, 2015	$ 397.1	$ 0.2	$ (26.8)	$ 240.8	$ 200.4	$ (17.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	54.7				54.7
Other comprehensive loss	(7.1)					(7.1)
Excercise of stock options	3.5			3.5
Share-based compensation	5.1			5.1
Repurchase of stock	(19.5)		(19.5)
Repurchase of stock - adjustments to APIC				0.0
Balances at end of period at Sep. 30, 2016	433.8	0.2	(46.3)	249.4	255.1	(24.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6.4				6.4
Other comprehensive loss	0.1					0.1
Excercise of stock options	3.3			3.3
Share-based compensation	6.3			6.3
Balances at end 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	55.5				55.5
Other comprehensive loss	(8.6)					(8.6)
Excercise of stock options	1.9			1.9
Share-based compensation	6.6			6.6
Balances at end of period at Sep. 30, 2018	$ 505.3	$ 0.2	$ (46.3)	$ 267.5	$ 317.0	$ (33.1)