Employee Benefit Plans (Components of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2017	Sep. 25, 2016	Sep. 24, 2017	Sep. 25, 2016
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7,896	$ 8,359	$ 23,688	$ 25,077
Interest cost	21,269	22,707	63,807	68,121
Expected return on plan assets	(35,345)	(36,445)	(106,035)	(109,335)
Amortization of unrecognized: Prior service cost	256	255	764	765
Amortization of unrecognized: Net loss	10,998	11,588	32,994	34,764
Settlement loss	0	300	0	900
Net periodic benefit cost	5,074	6,764	15,218	20,292
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,875	1,870	5,625	5,610
Interest cost	3,412	3,704	10,236	11,112
Expected return on plan assets	(3,156)	(3,017)	(9,468)	(9,051)
Amortization of unrecognized: Prior service cost	(543)	(701)	(1,629)	(2,103)
Amortization of unrecognized: Net loss	815	884	2,445	2,652
Net periodic benefit cost	$ 2,403	$ 2,740	$ 7,209	$ 8,220