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	105.7				105.7
Other comprehensive gain (loss), net of tax	(18.3)					(18.3)
Exercise of stock options	5.9			5.9
Share-based compensation	8.3			8.3
Ending balance at Mar. 31, 2022	1,005.6	0.2	(69.3)	329.9	788.2	(43.4)
Beginning balance at Dec. 31, 2021	953.0	0.2	(69.3)	324.4	724.2	(26.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	64.0				64.0
Other comprehensive gain (loss), net of tax	(16.9)					(16.9)
Exercise of stock options	1.3			1.3
Share-based compensation	4.2			4.2
Ending balance at Mar. 31, 2022	1,005.6	0.2	(69.3)	329.9	788.2	(43.4)
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	118.3				118.3
Other comprehensive gain (loss), net of tax	40.4					40.4
Exercise of stock options	3.6			3.6
Share-based compensation	14.9			14.9
Ending balance at Mar. 31, 2023	1,247.3	0.2	(69.3)	358.7	1,007.9	(50.2)
Beginning balance at Dec. 31, 2022	1,176.6	0.2	(69.3)	347.2	966.2	(67.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41.7				41.7
Other comprehensive gain (loss), net of tax	17.5					17.5
Exercise of stock options	2.1			2.1
Share-based compensation	9.4			9.4
Ending balance at Mar. 31, 2023	$ 1,247.3	$ 0.2	$ (69.3)	$ 358.7	$ 1,007.9	$ (50.2)