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, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 82.4	$ 68.7
Average basic shares outstanding	59.8	59.7
Effect of dilutive stock options	0.9	1.3
Average diluted shares outstanding	60.7	61.0
Earnings per share - basic:
Net income attributable to common shareholders	$ 1.38	$ 1.15
Earnings per share - diluted:
Net income attributable to common shareholders	$ 1.36	$ 1.13