Employee Benefit Plans (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
Components of net periodic benefit costs:
Service cost	$ 532	$ 516	$ 1,596	$ 1,548
Interest cost	2,026	2,201	6,078	6,603
Expected return on plan assets	(1,629)	(1,509)	(4,887)	(4,527)
Amortization of unrecognized net loss	1,157	951	3,471	2,853
Amortization of prior service cost	11	11	33	33
Net periodic benefit costs	$ 2,097	$ 2,170	$ 6,291	$ 6,510