Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating Lease, Weighted Average Remaining Lease Term	6 years 4 months 24 days
Operating Lease, Cost	$ 25.0	$ 25.1	$ 25.1
Operating Lease, Weighted Average Discount Rate, Percent	2.60%
Capitalized Right of Use Assets during the Period	$ 28.0
Right of Use Asset, Reduction due to Lease Termination	13.2
Operating Lease, Payments	$ 22.6