Pensions and Post-Retirement Benefit Plans - Components of Net Periodic Benefit Cost for Pension Plans (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Postemployment Benefits [Abstract]
Service cost	$ 0.3	$ 0.4
Interest cost	1.6	2.0
Expected return on plan assets	(2.0)	(2.0)
Amortization of net loss	0.4	0.4
Net periodic benefit cost	0.3	0.8
Defined contribution plan expense	$ 1.6	$ 1.6