Earnings Per Share (Computation Of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 47.1	$ 41.6	$ 37.8	$ 51.9	$ 43.2	$ 43.7	$ 126.5	$ 138.8
Average basic shares outstanding (in shares)	57.2			56.8			57.1	56.8
Effect of dilutive share-based awards (in shares)	0.6			0.7			0.7	0.6
Average diluted shares outstanding (in shares)	57.8			57.5			57.8	57.4
Earnings per basic share (in dollars per share)	$ 0.82			$ 0.91			$ 2.21	$ 2.44
Earnings per diluted share (in dollars per share)	$ 0.81			$ 0.90			$ 2.19	$ 2.42