Benefit Obligations - Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jul. 01, 2012	Jun. 30, 2013	Jul. 01, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 119	$ 116	$ 242	$ 225
Interest cost	14,363	15,483	28,633	30,735
Expected return on plan assets	(16,575)	(17,030)	(33,156)	(34,053)
Net actuarial loss, prior service cost and transition asset amortization	4,900	3,693	9,569	7,162
Total benefit cost	2,807	2,262	5,288	4,069
Post-retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	20	30	45
Interest cost	583	643	1,183	1,293
Expected return on plan assets	(902)	(856)	(1,777)	(1,906)
Net actuarial loss, prior service cost and transition asset amortization	353	490	728	990
Total benefit cost	$ 39	$ 297	$ 164	$ 422