Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Retirement Benefits [Abstract]
Service cost	$ 0.6	$ 0.7	$ 1.2	$ 1.4
Interest cost	0.6	0.5	1.2	1.0
Expected return on plan assets	(0.1)	(0.1)	(0.2)	(0.2)
Net periodic benefit cost	$ 1.1	$ 1.1	$ 2.2	$ 2.2