Employee Benefit Plans (Components of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2018	Mar. 26, 2017
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,155	$ 7,896
Interest cost	20,590	21,269
Expected return on plan assets	(36,891)	(35,345)
Amortization of unrecognized: Prior service cost	(106)	254
Amortization of unrecognized: Net loss	15,819	10,998
Curtailment loss	1,018	0
Net periodic benefit cost	8,585	5,072
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,812	1,875
Interest cost	2,897	3,412
Expected return on plan assets	(3,541)	(3,156)
Amortization of unrecognized: Prior service cost	(460)	(543)
Amortization of unrecognized: Net loss	454	815
Net periodic benefit cost	$ 1,162	$ 2,403