Earnings Per Share - Computation of Basic and Diluted Net EPS (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net earnings attributable to controlling interests	$ 105.1	$ 130.4	$ 171.9	$ 55.7	$ 95.1	$ 122.8	$ 150.0	$ 46.5	$ 463.1	$ 414.4	$ 356.8
Weighted average number of common shares outstanding									180.1	177.6	172.2
Dilutive effect of stock options using the treasury stock method									2.0	0.8	1.0
Weighted average number of common and common equivalent shares outstanding									182.1	178.4	173.2
Basic net earnings per share									$ 2.57	$ 2.33	$ 2.07
Diluted net earnings per share									$ 2.54	$ 2.32	$ 2.06