Summary of Significant Accounting Policies - Effect of Immaterial Changes to Presentation of Consolidated Statement of Earnings (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating expense									$ 840.7	$ 743.1	$ 535.9
Earnings before income taxes	$ 28.4	$ 105.7	$ 128.5	$ 30.9	$ 30.3	$ 95.4	$ 111.9	$ 53.9	293.5	291.5	291.0
Provision (benefit) for income taxes									(95.6)	(36.0)	6.4
Net earnings									389.1	327.5	284.6
Net earnings attributable to noncontrolling interests									(32.3)	(24.1)	(16.0)
Net earnings attributable to controlling interests	$ 62.3	$ 133.3	$ 139.3	$ 21.9	$ 51.5	$ 93.6	$ 109.0	$ 49.3	$ 356.8	$ 303.4	$ 268.6
Basic net earnings per share									$ 2.07	$ 1.98	$ 2.08
Diluted net earnings per share									$ 2.06	$ 1.97	$ 2.06
As Previously Reported [Member]
Operating expense										$ 767.2	$ 552.4
Earnings before income taxes										267.4	274.5
Provision (benefit) for income taxes										(36.0)	5.9
Net earnings										$ 303.4	$ 268.6
Basic net earnings per share										$ 1.98	$ 2.08
Diluted net earnings per share										$ 1.97	$ 2.06
As Restated [Member]
Operating expense										$ 743.1	$ 535.9
Earnings before income taxes										291.5	291.0
Provision (benefit) for income taxes										(36.0)	6.4
Net earnings										327.5	284.6
Net earnings attributable to noncontrolling interests										24.1	16.0
Net earnings attributable to controlling interests										$ 303.4	$ 268.6
Basic net earnings per share										$ 1.98	$ 2.08
Diluted net earnings per share										$ 1.97	$ 2.06