Pension and Other Postretirement Obligations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 01, 2012	Apr. 03, 2011
Pension Obligations [Member]
Components of net periodic benefit cost :
Service cost	$ 1,432	$ 1,349
Interest cost	3,010	2,811
Expected return on plan assets	(3,165)	(2,860)
Amortization of prior service credit	(19)	(36)
Net loss recognition	1,492	1,543
Net periodic benefit cost	2,750	2,807
Other Postretirement Obligations [Member]
Components of net periodic benefit cost :
Service cost	32	40
Interest cost	588	681
Expected return on plan assets
Amortization of prior service credit	(29)	(60)
Net loss recognition	262	119
Net periodic benefit cost	$ 853	$ 780