Income Taxes - Components of Income Tax Provision (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
Federal	$ 79.6	$ 57.6	$ 44.7
State and local	14.3	1.2	8.4
Foreign	106.0	67.3	49.0
Total current expense	199.9	126.1	102.1
Deferred tax expense (benefit):
Federal	130.1	(15.8)	10.7
State and local	5.3	3.6	10.9
Foreign	(4.8)	(18.3)	8.9
Total deferred tax expense (benefit)	130.6	(30.5)	30.5
Total income tax provision	$ 330.5	$ 95.6	$ 132.6