Computations of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net earnings	$ 102.2	$ 92.7	$ 319.8	$ 275.0
Basic weighted average common shares	103.9	103.2	103.9	103.2
Effect of dilutive stock options and employee stock purchase plan shares	0.1	0.1	0.1	0.1
Effect of restricted shares issued	0.6	0.7	0.5	0.6
Diluted weighted average common shares	104.6	104.0	104.5	103.9
Basic net earnings per common share	$ 0.98	$ 0.90	$ 3.08	$ 2.67
Diluted net earnings per common share	$ 0.98	$ 0.89	$ 3.06	$ 2.65