Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8.0	$ 6.6	$ 7.8
Interest cost	4.2	4.1	3.9
Expected return on plan assets	(1.5)	(1.5)	(1.6)
Net actuarial (gain) loss	(7.4)	17.2	(2.4)
Net periodic benefit expense	3.3	26.4	7.7
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	10.3	11.2	14.0
Interest cost	16.3	16.4	14.9
Expected return on plan assets	(11.5)	(11.4)	(10.0)
Net actuarial (gain) loss	9.1	(12.4)	(18.0)
Net periodic benefit expense	$ 24.2	$ 3.8	$ 0.9