Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2025	Mar. 31, 2024
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 31.6	$ 16.5	$ 45.0	$ 38.2	$ 48.1	$ 83.2
Weighted average number of common shares	50,795,094		50,147,639		50,807,945	50,106,735
Dilutive effect of stock-based compensation	251,630		479,318		258,376	437,784
Adjusted weighted average number of common shares	51,046,724		50,626,957		51,066,321	50,544,519
Basic net income per common share	$ 0.62		$ 0.90		$ 0.95	$ 1.66
Diluted net income per common share	$ 0.62		$ 0.89		$ 0.94	$ 1.65
Retained Earnings
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 31.6	$ 16.5	$ 45.0	$ 38.2