Employee Benefit Plans (Components of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2016	Sep. 27, 2015	Sep. 25, 2016	Sep. 27, 2015
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,359	$ 10,010	$ 25,077	$ 30,030
Interest cost	22,707	21,836	68,121	65,508
Expected return on plan assets	(36,445)	(36,232)	(109,335)	(108,696)
Amortization of unrecognized: Prior service cost	255	109	765	327
Amortization of unrecognized: Net loss	11,588	13,678	34,764	41,031
Settlement loss	300	0	900	0
Net periodic benefit cost	6,764	9,401	20,292	28,200
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,870	2,065	5,610	6,195
Interest cost	3,704	3,541	11,112	10,623
Expected return on plan assets	(3,017)	(2,877)	(9,051)	(8,631)
Amortization of unrecognized: Prior service cost	(701)	(804)	(2,103)	(2,412)
Amortization of unrecognized: Net loss	884	993	2,652	2,979
Net periodic benefit cost	$ 2,740	$ 2,918	$ 8,220	$ 8,754