Employee Benefit Plans (Components of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2016	Jun. 28, 2015	Jun. 26, 2016	Jun. 28, 2015
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,359	$ 10,010	$ 16,718	$ 20,020
Interest cost	22,707	21,836	45,414	43,672
Expected return on plan assets	(36,445)	(36,232)	(72,890)	(72,465)
Amortization of unrecognized: Prior service cost	255	109	510	218
Amortization of unrecognized: Net loss	11,588	13,677	23,176	27,354
Settlement loss	300	0	600	0
Net periodic benefit cost	6,764	9,400	13,528	18,799
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,870	2,065	3,740	4,130
Interest cost	3,704	3,541	7,408	7,082
Expected return on plan assets	(3,017)	(2,877)	(6,034)	(5,754)
Amortization of unrecognized: Prior service cost	(701)	(804)	(1,402)	(1,608)
Amortization of unrecognized: Net loss	884	993	1,768	1,986
Net periodic benefit cost	$ 2,740	$ 2,918	$ 5,480	$ 5,836