Benefit Plans - Reconciliations of Benefit Obligations, Fair Value of Plan Assets and Funded Status of Pension Plans and Other Post-Retirement Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in plan assets
Fair value of plan assets beginning of year	$ 390.1
Fair value of plan assets end of year	425.7	$ 390.1
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Benefits Paid	3.0	3.1
Change in benefit obligations
Benefit obligation beginning of year	36.9	38.8
Service cost	0.2	0.2
Interest cost	1.3	1.5
Actuarial loss	0.2	(0.5)
Translation (gain) loss	0.0	0.0
Benefit obligation end of year	35.6	36.9	$ 38.8
Change in plan assets
Fair value of plan assets beginning of year	0.0	0.0
Actual return on plan assets	0.0	0.0
Company contributions	2.9	3.1
Translation gain (loss)	0.0	0.0
Fair value of plan assets end of year	0.0	0.0	0.0
Funded status
Plan assets less than benefit obligation	(35.6)	(36.9)
Defined Benefit Plan, Plan Assets, Benefits Paid	2.9	3.1
U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Benefits Paid	16.9	12.1
Change in benefit obligations
Benefit obligation beginning of year	413.3	396.9
Service cost	10.3	11.2	14.0
Interest cost	16.3	16.4	14.9
Actuarial loss	40.0	0.9
Translation (gain) loss	0.0	0.0
Benefit obligation end of year	463.0	413.3	396.9
Change in plan assets
Fair value of plan assets beginning of year	344.4	327.7
Actual return on plan assets	42.4	24.6
Company contributions	4.6	4.2
Translation gain (loss)	0.0	0.0
Fair value of plan assets end of year	374.5	344.4	327.7
Funded status
Plan assets less than benefit obligation	(88.5)	(68.9)
Defined Benefit Plan, Plan Assets, Benefits Paid	16.9	12.1
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Benefits Paid	7.0	4.9
Change in benefit obligations
Benefit obligation beginning of year	186.8	173.4
Service cost	8.0	6.6	7.8
Interest cost	4.2	4.1	3.9
Actuarial loss	(8.5)	16.8
Translation (gain) loss	23.7	(9.2)
Benefit obligation end of year	207.2	186.8	173.4
Change in plan assets
Fair value of plan assets beginning of year	45.7	46.6
Actual return on plan assets	2.1	3.0
Company contributions	8.2	5.8
Translation gain (loss)	3.7	(4.8)
Fair value of plan assets end of year	51.2	45.7	$ 46.6
Funded status
Plan assets less than benefit obligation	(156.0)	(141.1)
Defined Benefit Plan, Plan Assets, Benefits Paid	$ 8.5	$ 4.9