Pension and Post-Employment Benefits - Plan Net Pension Credit (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ (3.9)	$ (3.9)
Expected return on plan assets	5.6	5.7
Amortization of prior service credit	0.2	0.3
Amortization of actuarial net losses	0.0	(0.5)
Net pension credit total	1.9	1.6
Germany [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	(0.1)	(0.1)
Amortization of actuarial net losses	(0.1)	(0.1)
Net pension credit total	$ (0.2)	$ (0.2)