Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2013	Sep. 29, 2012	Sep. 28, 2013	Sep. 29, 2012
Pension benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 350	$ 339	$ 1,051	$ 1,016
Interest cost	2,023	2,185	6,070	6,556
Expected return on plan assets	(2,845)	(2,721)	(8,535)	(8,165)
Amortization of prior service cost (credit)	1	1	1	1
Amortization of net gain (loss)	984	966	2,954	2,900
Net periodic benefit cost	513	770	1,541	2,308
Other benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	69	67	207	200
Interest cost	155	278	467	835
Amortization of prior service cost (credit)	2	0	5	(1)
Amortization of net gain (loss)	(41)	(7)	(125)	(20)
Net periodic benefit cost	$ 185	$ 338	$ 554	$ 1,014