Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss, net
Beginning balance at Sep. 30, 2021	$ 904.0	$ 0.2	$ (69.3)	$ 315.7	$ 682.5	$ (25.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41.7				41.7
Other comprehensive gain (loss), net of tax	(1.4)					(1.4)
Exercise of stock options	4.6			4.6
Share-based compensation	4.1			4.1
Ending balance at Dec. 31, 2021	953.0	0.2	(69.3)	324.4	724.2	(26.5)
Beginning balance at Sep. 30, 2022	1,070.1	0.2	(69.3)	340.2	889.6	(90.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	76.6				76.6
Other comprehensive gain (loss), net of tax	22.9					22.9
Exercise of stock options	1.5			1.5
Share-based compensation	5.5			5.5
Ending balance at Dec. 31, 2022	$ 1,176.6	$ 0.2	$ (69.3)	$ 347.2	$ 966.2	$ (67.7)