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, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 55.0	$ 51.1
Average basic shares outstanding	58.2	58.1
Effect of dilutive stock options	0.7	0.8
Average diluted shares outstanding	58.9	58.9
Earnings per share - basic:
Net income attributable to common shareholders	$ 0.95	$ 0.88
Earnings per share - diluted:
Net income attributable to common shareholders	$ 0.93	$ 0.87