Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Pension benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 326	$ 317	$ 701	$ 677
Interest cost	2,017	2,152	4,047	4,371
Expected return on plan assets	(2,892)	(2,731)	(5,690)	(5,444)
Amortization of prior service cost (credit)	978	991	1,970	1,934
Net periodic benefit cost	429	729	1,028	1,538
Other benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	70	58	138	133
Interest cost	32	248	312	557
Amortization of prior service cost (credit)	1	(1)	3	(1)
Amortization of net (gain) loss	(58)	(16)	(84)	(13)
Net periodic benefit cost	$ 45	$ 289	$ 369	$ 676