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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 69.2	$ 68.2	$ 132.3	$ 123.3
Average basic shares outstanding	59.5	58.3	59.4	58.3
Effect of dilutive stock options	1.0	0.9	1.0	0.7
Average diluted shares outstanding	60.5	59.2	60.4	59.0
Earnings per share - basic:
Net income attributable to common shareholders	$ 1.16	$ 1.17	$ 2.23	$ 2.11
Earnings per share - diluted:
Net income attributable to common shareholders	$ 1.14	$ 1.15	$ 2.19	$ 2.09