Retirement Plans - Components of Net Periodic Benefit (Credits) Costs for Pension and Other Postretirement Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 561	$ 506	$ 1,134	$ 1,012
Interest cost	8,881	10,139	17,662	20,277
Expected return on plan assets	(12,818)	(11,964)	(25,598)	(23,928)
Amortization of prior service cost	1	34	2	69
Amortization of net loss (gain)	770	1,050	1,616	2,101
Settlements	0	2,000	0	2,000
Net periodic (credits) benefit costs	(2,605)	1,765	(5,184)	1,531
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	9	17	19
Interest cost	59	72	118	144
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	1	2	3	3
Amortization of net loss (gain)	(39)	(13)	(78)	(26)
Settlements	0	0	0	0
Net periodic (credits) benefit costs	$ 29	$ 70	$ 60	$ 140