Leases - Summary of Components of Lease Expense (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Operating lease expense	$ 6.5	$ 19.7
Sublease income	(1.4)	(3.9)
Net lease expense	$ 5.1	$ 15.8