Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2019
Rent expense for operating leases	$ 11.7		$ 8.1	$ 30.0	$ 24.4
Operating Lease, Right-of-Use Asset	299.5			299.5		$ 170.5
Operating Lease, Liability	$ 325.3			$ 325.3		$ 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