Net Income Per Unrestricted Share - Reconciliation of Numerator and Denominator Used in Calculation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Income	$ 99.7	$ 71.3
Weighted-Average Unrestricted Shares Outstanding (in shares)	63,886,700	64,254,500
Equity-based Compensation Equivalent Shares (in shares)	766,100	518,300
Weighted-Average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution (in shares)	64,652,800	64,772,800
Basic Net Income Per Unrestricted Share (in shares)	$ 1.56	$ 1.11
Diluted Net Income Per Unrestricted Share (in shares)	$ 1.54	$ 1.10