Pensions and Other Post-retirement Benefits - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Estimated contributions by employer to pension plans	$ 7,600
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%	4.50%
Increase in costs of covered health care benefits	6.50%
Percentage of change in assumed health care cost trend rate	1.00%
Increase or decrease in other postretirement obligations	$ 1,000
Increase or decrease in current year plan expense	100
Defined contribution pension plan expense	8,300	$ 9,000	$ 8,100
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	3,382	5,901	18,526
Service cost	10,342	11,125	11,023
Estimated benefit payments, year one	25,000
Estimated benefit payments, year two	25,600
Estimated benefit payments, year three	26,500
Estimated benefit payments, year four	27,600
Estimated benefit payments, year five	28,100
Estimated benefit payments, five years thereafter	151,000
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1,814	1,509	516
Service cost	354	$ 369	$ 403
Estimated benefit payments, year one	2,400
Estimated benefit payments, year two	2,500
Estimated benefit payments, year three	2,300
Estimated benefit payments, year four	2,000
Estimated benefit payments, year five	2,100
Estimated benefit payments, five years thereafter	8,900
Change in Assumptions for Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 1,800