Employee Benefit Plans (Components Of Net Periodic Benefit Costs) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 25, 2011	Sep. 30, 2012	Sep. 25, 2011
Pension And SERPA Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,420	$ 9,274	$ 25,260	$ 27,819
Interest cost	20,816	20,147	62,448	60,441
Expected return on plan assets	(29,277)	(26,652)	(87,832)	(79,959)
Prior service cost	740	746	2,219	2,235
Net loss	10,969	7,550	32,906	22,659
Curtailment loss	0	0	0	236
Net periodic benefit cost	11,668	11,065	35,001	33,431
Postretirement Healthcare Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,854	1,907	5,560	5,721
Interest cost	4,578	4,911	13,733	14,733
Expected return on plan assets	(2,356)	(2,346)	(7,068)	(7,038)
Prior service cost	(963)	(969)	(2,890)	(2,907)
Net loss	1,855	1,798	5,566	5,394
Net periodic benefit cost	$ 4,968	$ 5,301	$ 14,901	$ 15,903