Pension and Postretirement Benefit Obligations - Components of Net Periodic Postretirement Benefit Cost (Detail) - Net Postretirement Benefits Activity [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 502	$ 572	$ 1,507	$ 1,716
Interest cost	696	910	2,088	2,732
Recognized net actuarial loss	499	648	1,497	1,944
Amortization of prior service cost	(462)	(745)	(1,386)	(2,237)
Net periodic benefit cost	$ 1,235	$ 1,385	$ 3,706	$ 4,155