Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 68.2	$ 55.8	$ 123.3	$ 106.8
Average basic shares outstanding	58.3	58.0	58.3	58.0
Effect of dilutive stock options	0.9	0.8	0.7	0.8
Average diluted shares outstanding	59.2	58.8	59.0	58.8
Earnings per share - basic:
Net income attributable to common shareholders	$ 1.17	$ 0.96	$ 2.11	$ 1.84
Earnings per share - diluted:
Net income attributable to common shareholders	$ 1.15	$ 0.95	$ 2.09	$ 1.82