Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 29, 2014	Mar. 30, 2013
Components of net periodic benefit costs:
Service cost	$ 333	$ 532
Interest cost	2,205	1,967
Expected return on plan assets	(1,756)	(1,629)
Amortization of unrecognized net loss	821	1,147
Amortization of prior service cost	11	11
Net periodic benefit costs	$ 1,614	$ 2,028