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, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
Net income	$ 98.0	$ 83.6
Weighted average number of shares outstanding, basic (in shares)	35.5	36.3
Add: Potential effect of dilutive securities attributable to stock-based payments	0.1	0.2
Weighted-average shares outstanding – diluted	35.6	36.5
Earnings per share - Basic (in dollars per share)	$ 2.76	$ 2.30
Earnings per share - Diluted (in dollars per share)	$ 2.75	$ 2.29