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, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 108.4	$ 62.8
Net income before allocation to noncontrolling interests	$ 108.4	$ 62.8
Average basic shares outstanding (in shares)	58.2	58.8
Effect of dilutive stock options	0.7	0.8
Average diluted shares outstanding (in shares)	58.9	59.6
Earnings per share - basic:
Net income attributable to common shareholders	$ 1.86	$ 1.07
Earnings per share - diluted:
Net income attributable to common shareholders	$ 1.84	$ 1.05