Pensions and Post-Retirement Benefit Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Plan	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of domestic non-qualified defined benefit plans | Plan	3
Pension settlement charge	$ 0.0	$ (10.0)	$ (4.4)
Defined contribution plan expense	7.5	8.9	7.8
Net actuarial gain	13.2
Accumulated benefit obligation, pension plans	201.3	218.7
Operating expenses	$ 10.3	11.2	10.4
Growth seeking assets [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation investment strategy	30.00%
Growth seeking assets [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation investment strategy	40.00%
Income generating assets [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation investment strategy	60.00%
Income generating assets [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation investment strategy	70.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Retiree pension obligations	$ 201.7	219.1	243.6
Net actuarial gain	13.2	(7.3)
Expected contributions by employer	2.7
Pension Benefits [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension settlement charge		(10.0)	(4.4)
Pension Benefits [Member] | United States [Member] | Qualified Plan [Member] | Annuitize [Member]
Defined Benefit Plan Disclosure [Line Items]
Retiree pension obligations		31.3
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Retiree pension obligations	9.4	11.1	$ 10.0
Net actuarial gain	1.7	$ (1.5)
Expected contributions by employer	$ 0.9
Salaried and Hourly Employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of domestic non-qualified defined benefit plans | Plan	2