Pension and Other Postretirement Obligations - Components of Net Periodic Benefit Costs (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 Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,676	$ 1,432	$ 3,364	$ 2,864
Interest cost	2,914	3,037	5,862	6,047
Expected return on plan assets	(3,391)	(3,169)	(6,797)	(6,333)
Amortization of prior service credit	(8)	(19)	(16)	(39)
Actuarial losses	1,665	1,490	3,333	2,982
Net periodic benefit cost	2,856	2,771	5,746	5,521
Other Postretirement Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	35	30	68	62
Interest cost	557	545	1,083	1,133
Amortization of prior service credit	(28)	(29)	(55)	(58)
Actuarial losses	320	223	598	485
Net periodic benefit cost	$ 884	$ 769	$ 1,694	$ 1,622