Employee Benefit Plans (Components of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2017	Mar. 27, 2016
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7,896	$ 8,359
Interest cost	21,269	22,707
Expected return on plan assets	(35,345)	(36,445)
Amortization of unrecognized: Prior service cost	254	255
Amortization of unrecognized: Net loss	10,998	11,587
Settlement loss	0	300
Net periodic benefit cost	5,072	6,763
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,875	1,870
Interest cost	3,412	3,704
Expected return on plan assets	(3,156)	(3,017)
Amortization of unrecognized: Prior service cost	(543)	(701)
Amortization of unrecognized: Net loss	815	884
Net periodic benefit cost	$ 2,403	$ 2,740