Postretirement Benefit Costs for Health Care and Life Insurance (Detail) (Other Postretirement Benefit Plans, Defined Benefit, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 25, 2012	Mar. 27, 2011
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost-benefits earned during the period	$ 175	$ 175
Interest cost on net benefit obligation	2,050	2,375
Amortization of prior service credit	(4,800)	(4,875)
Amortization of actuarial loss	650	1,200
Net periodic cost (benefit)	$ (1,925)	$ (1,125)