Valuation and Qualifying Accounts - Summary of Activity for Valuation Allowances (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Abstract]
Beginning balance, Accounts receivable allowance	$ (36.6)	$ (25.7)	$ (27.5)
Charged to costs and expenses, Accounts receivable allowance	(18.8)	(19.6)	(6.2)
Deductions, Accounts receivable allowance	11.9	8.7	8.0
Ending balance, Accounts receivable allowance	(43.5)	(36.6)	(25.7)
Beginning balance, Deferred tax assets valuation allowance	(12.8)	(3.2)	(4.3)
Charged to costs and expenses, Deferred Tax Allownces	(10.3)	(9.9)	(0.9)
Deductions, Deferred tax assets valuation allowance	0.7	0.3	2.0
Ending balance, Deferred tax assets valuation allowance	$ (22.4)	$ (12.8)	$ (3.2)