Retirement Plans and Other Post-Retirement Benefits - Schedule of Change in Benefit Obligation and Plan Assets (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 at beginning of year	$ 610.7
Fair value of plan assets at end of year	673.1	$ 610.7
Pension Benefits [Member]
Change in Benefit Obligation
Balance at beginning of year	552.0	541.9
Service cost	10.7	10.5	$ 11.6
Interest cost	23.8	24.5	23.3
Plan amendments	4.1	5.5
Actuarial (gain)/loss	45.5	17.0
Benefits paid	(36.5)	(22.9)
One-time settlement		(24.2)
Effect of currency rate changes	1.2	(0.3)
Balance at end of year	600.8	552.0	541.9
Change in Plan Assets
Fair value of plan assets at beginning of year	610.7	594.9
Actual return on plan assets	96.8	60.8
Total contributions	2.1	2.1
Benefits paid	(36.5)	(22.9)
One-time settlement		(24.2)
Fair value of plan assets at end of year	673.1	610.7	594.9
Funded status at end of year	72.3	58.7
Other Benefits [Member]
Change in Benefit Obligation
Balance at beginning of year	47.9	51.0
Service cost	1.2	1.1	1.4
Interest cost	2.0	2.0	2.0
Participant contributions	1.1	1.0
Actuarial (gain)/loss	1.5	(3.4)
Benefits paid	(3.0)	(3.8)
Balance at end of year	50.7	47.9	$ 51.0
Change in Plan Assets
Total contributions	3.0	3.8
Benefits paid	(3.0)	(3.8)
Funded status at end of year	$ (50.7)	$ (47.9)