Income Taxes - Summary of Changes in Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gross Unrecognized Tax Benefits
Balance at beginning of period	$ 33.2	$ 29.5	$ 30.4
Additions based on tax positions related to current year	7.9	5.4	4.0
Additions based on tax positions related to prior years	0.1
Reductions based on tax positions related to prior years		(0.3)	(0.9)
Settlements	0.0	(0.8)	0.0
Statute expirations	(2.7)	(2.2)	(2.9)
Foreign currency translation	(1.8)		(1.1)
Foreign currency translation		1.6
Balance at end of period	$ 36.7	$ 33.2	$ 29.5