Earnings Per Share (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Earnings Per Share [Abstract]
Net income	$ 120.3	$ 124.3
Weighted average number of shares outstanding, basic (in shares)	35.5	35.6
Add: Potential effect of dilutive securities attributable to stock-based payments	0.2	0.2
Weighted-average shares outstanding – diluted	35.7	35.8
Earnings per share - Basic (in dollars per share)	$ 3.39	$ 3.49
Earnings per share - Diluted (in dollars per share)	$ 3.37	$ 3.47