Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2013	Mar. 31, 2012
Pension benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 375	$ 360
Interest cost	2,030	2,219
Expected return on plan assets	(2,798)	(2,713)
Amortization of net (gain) loss	992	943
Net periodic benefit cost	599	809
Other benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	68	75
Interest cost	280	309
Amortization of prior service cost (credit)	2	0
Amortization of net (gain) loss	(26)	3
Net periodic benefit cost	$ 324	$ 387