Employee Benefit Plans (Components of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jun. 25, 2017	Jul. 01, 2018	Jun. 25, 2017
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,063	$ 7,896	$ 16,218	$ 15,792
Interest cost	20,729	21,269	41,319	42,538
Expected return on plan assets	(36,926)	(35,345)	(73,817)	(70,690)
Amortization of unrecognized: Prior service cost	(105)	254	(211)	508
Amortization of unrecognized: Net loss	16,318	10,998	32,137	21,996
Curtailment loss	0	0	1,018	0
Net periodic benefit cost	8,079	5,072	16,664	10,144
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,789	1,875	3,601	3,750
Interest cost	2,886	3,412	5,783	6,824
Expected return on plan assets	(3,541)	(3,156)	(7,082)	(6,312)
Amortization of unrecognized: Prior service cost	(460)	(543)	(920)	(1,086)
Amortization of unrecognized: Net loss	454	815	908	1,630
Net periodic benefit cost	$ 1,128	$ 2,403	$ 2,290	$ 4,806