Pensions and Other Post-retirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Period of amortization for actuarial gains and losses	10 years
Estimated contributions by employer to pension plans	$ 6.2
Percentage increase in health care benefit cost	6.50%
Percentage decrease in health care benefits for successive year	0.50%	0.50%
Estimated future percentage of health care benefits	4.50%
Percentage of change in assumed health care cost trend rate	1.00%
Increase or decrease in other postretirement obligations	$ 1.1
Increase or decrease in current year plan expense	1.0
Defined contribution pension plan expense	6.8	$ 6.5	$ 5.8
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Estimated benefit payments, 2016	20.2
Estimated benefit payments, 2017	21.0
Estimated benefit payments, 2018	22.0
Estimated benefit payments, 2019	22.7
Estimated benefit payments, 2020	24.3
Estimated benefit payments, five years thereafter	139.2
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Estimated benefit payments, 2016	1.4
Estimated benefit payments, 2017	1.5
Estimated benefit payments, 2018	1.7
Estimated benefit payments, 2019	1.8
Estimated benefit payments, 2020	1.8
Estimated benefit payments, five years thereafter	$ 8.5