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, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 51.9	$ 43.2	$ 43.7	$ 44.6	$ 48.8	$ 49.5	$ 138.8	$ 142.9
Average basic shares outstanding (in shares)	56.8			56.7			56.8	56.7
Effect of dilutive share-based awards (in shares)	0.7			0.0			0.6	0.0
Average diluted shares outstanding (in shares)	57.5			56.7			57.4	56.7
Earnings per basic share (in dollars per share)	$ 0.91			$ 0.79			$ 2.44	$ 2.52
Earnings per diluted share (in dollars per share)	$ 0.90			$ 0.79			$ 2.42	$ 2.52