Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2013 plan	Mar. 31, 2012
Employee Benefits
Number of defined benefit plans	2
Components of net periodic benefit cost:
Service cost	$ 2,421	$ 2,226
Interest cost	2,068	2,258
Expected return on plan assets	(1,612)	(1,592)
Amortization and other	1,636	1,530
Net periodic benefit cost	4,513	4,422
Defined benefit pension plan
Target allocation and pension plan asset allocation
Contributions expected to be made to defined benefit pension plans	$ 0