Consolidated Statements of Shareholders’ Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock, Common [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balances at beginning of period at Sep. 30, 2014	$ 345.4	$ 0.2	$ (17.5)	$ 229.6		$ 144.7	$ (11.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	55.7					55.7
Other comprehensive loss	(5.9)						(5.9)
Excercise of stock options	3.0			3.0
Share-based compensation	3.6			3.6
Repurchase of stock	(4.7)		(4.5)
Repurchase of stock - adjustments to APIC				(0.2)
Stock held in escrow for business combination				4.8	$ (4.8)
Balances at end 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)