Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.8	$ 2.6
Interest cost	3.0	4.1
Expected return on plan assets	(2.2)	(2.9)
Net periodic benefit cost	1.6	3.8
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.8	1.8
Interest cost	1.1	0.9
Expected return on plan assets	(0.4)	(0.3)
Net periodic benefit cost	$ 2.5	$ 2.4