Employee Benefit Plans (Components Of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2016	Mar. 29, 2015
Pension Plans and Supplemental Employee Retirement Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,359	$ 10,010
Interest cost	22,707	21,836
Expected return on plan assets	(36,445)	(36,232)
Prior service cost	255	109
Net loss	11,587	13,677
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	300	0
Net periodic benefit cost	6,763	9,400
Postretirement Healthcare Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,870	2,065
Interest cost	3,704	3,541
Expected return on plan assets	(3,017)	(2,877)
Prior service cost	(701)	(804)
Net loss	884	993
Net periodic benefit cost	$ 2,740	$ 2,918