Income Taxes - Components of Earnings Before Income Taxes and Provision for Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Income Tax Disclosure [Abstract]
United States									$ 337.6	$ 274.1		$ 335.7
Foreign, principally Australia, Canada, New Zealand and the U.K.									141.8	85.7		(2.1)
Earnings before income taxes	$ 43.2	$ 90.3	$ 103.6	$ 242.3	$ 29.2	$ 76.9	$ 54.1	$ 199.6	479.4	359.8		333.6
Federal Current										7.1		40.2
Federal Deferred									(214.0)	(183.5)		(146.7)
Total Provision (benefit) for income taxes, Federal									(214.0)	(176.4)		(106.5)
State and local Current									15.4	11.6		7.2
State and local Deferred									(29.0)	(3.9)		(0.3)
Total Provision (benefit) for income taxes, State and local									(13.6)	7.7		6.9
Foreign Current									60.7	25.9		20.7
Foreign Deferred									(29.6)	(14.3)		(17.8)
Total Provision (benefit) for income taxes, Foreign									31.1	11.6		2.9
Benefit for income taxes									$ (196.5)	$ (157.1)	[1]	$ (96.7)	[1]

[1] See Note 3 - Revenues from Contracts with Customers for additional information about the restatements related to Topic 606.