Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jul. 02, 2011	Jun. 30, 2012	Jul. 02, 2011
Pension benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 317	$ 207	$ 677	$ 461
Interest cost	2,152	2,530	4,371	4,685
Expected return on plan assets	(2,731)	(2,919)	(5,444)	(5,571)
Amortization of prior service cost (credit)	0	1	0	1
Amortization of net loss (gain)	991	599	1,934	1,173
Net periodic benefit cost	729	418	1,538	749
Other benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	58	82	133	151
Interest cost	248	301	557	619
Amortization of prior service cost (credit)	(1)	(2)	(1)	(1)
Amortization of net loss (gain)	(16)	(31)	(13)	(6)
Net periodic benefit cost	$ 289	$ 350	$ 676	$ 763