Earnings per Common Share - Schedule of Calculations of Basic and Diluted Earnings (Loss) per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Earnings Per Share [Abstract]
Net income	$ 122.5	$ 84.8
Dividends allocated to participating securities	0.0	(0.1)
Earnings available for common stockholders used in calculation of basic earnings per common share	$ 122.5	$ 84.7
Weighted average number of common shares outstanding, basic (in shares)	50.1	50.1
Basic earnings per common share (in dollars per share)	$ 2.45	$ 1.69
Dividends allocated to participating securities	$ 0.0	$ (0.1)
Earnings available for common stockholders used in calculation of diluted earnings per common share	$ 122.5	$ 84.7
Effect of shares issuable under share-based compensation plans (in shares)	0.3	0.6
Weighted average number of common shares outstanding, diluted (in shares)	50.4	50.7
Diluted earnings per common share (in dollars per share)	$ 2.43	$ 1.67