Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
Rent expense for operating leases	$ 9.7	$ 8.1	$ 18.3	$ 16.3
Operating Lease, Right-of-Use Asset	284.5		284.5		$ 170.5
Operating Lease, Liability	291.7		$ 291.7		$ 174.4
Recognition of right of use asset related to the new corporate headquarters facility	121.7
Recognition of operating lease liability related to the new corporate headquarters facility	$ 121.7