Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 62.8	$ 82.4
Net income before allocation to noncontrolling interests	$ 62.8	$ 82.5
Average basic shares outstanding	58.8	59.8
Effect of dilutive stock options	0.8	0.9
Average diluted shares outstanding	59.6	60.7
Earnings per share - basic:
Net income attributable to common shareholders	$ 1.07	$ 1.38
Earnings per share - diluted:
Net income attributable to common shareholders	$ 1.05	$ 1.36