Employee Benefit Plans (Components of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2017	Jun. 26, 2016	Jun. 25, 2017	Jun. 26, 2016
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7,896	$ 8,359	$ 15,792	$ 16,718
Interest cost	21,269	22,707	42,538	45,414
Expected return on plan assets	(35,345)	(36,445)	(70,690)	(72,890)
Amortization of unrecognized: Prior service cost	254	255	508	510
Amortization of unrecognized: Net loss	10,998	11,588	21,996	23,176
Settlement loss	0	300	0	600
Net periodic benefit cost	5,072	6,764	10,144	13,528
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,875	1,870	3,750	3,740
Interest cost	3,412	3,704	6,824	7,408
Expected return on plan assets	(3,156)	(3,017)	(6,312)	(6,034)
Amortization of unrecognized: Prior service cost	(543)	(701)	(1,086)	(1,402)
Amortization of unrecognized: Net loss	815	884	1,630	1,768
Net periodic benefit cost	$ 2,403	$ 2,740	$ 4,806	$ 5,480