Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Service cost	$ 2.8	$ 3.3	$ 2.6
Interest cost	2.0	2.9	7.3
Expected return on plan assets	(0.5)	(0.8)	(3.9)
Net actuarial (gain) loss	(1.5)	6.8	(4.1)
Net periodic benefit expense	$ 2.8	$ 12.2	$ 1.9