Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common stock	Paid-in capital	Retained earnings	Accumulated other comprehensive income
Common stock outstanding, at beginning of period (shares) at Sep. 30, 2023		134.8
Balance at beginning of period at Sep. 30, 2023	$ 203.2	$ 1.3	$ 48.0	$ 140.7	$ 13.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31.9			31.9
Stock-based compensation, net of issuances (in shares)		0.2
Stock-based compensation, net of issuances	(1.7)		(1.7)
Repurchases of common stock (shares)		(5.4)
Repurchases of common stock	(172.8)			(172.8)
Other comprehensive loss, net of tax	4.2				4.2
Common stock outstanding, at end of period (shares) at Dec. 31, 2023		129.6
Balance at end of period at Dec. 31, 2023	$ 64.8	$ 1.3	46.3	(0.2)	17.4
Common stock outstanding, at beginning of period (shares) at Sep. 30, 2024	128.5	128.5
Balance at beginning of period at Sep. 30, 2024	$ 185.6	$ 1.3	51.2	123.2	9.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	91.6			91.6
Stock-based compensation, net of issuances (in shares)		0.1
Stock-based compensation, net of issuances	(0.9)		(0.9)
Repurchases of common stock (shares)		(1.0)
Repurchases of common stock	(39.6)			(39.6)
Other comprehensive loss, net of tax	$ (6.9)				(6.9)
Common stock outstanding, at end of period (shares) at Dec. 31, 2024	127.6	127.6
Balance at end of period at Dec. 31, 2024	$ 229.8	$ 1.3	$ 50.3	$ 175.2	$ 3.0