Pension and Postretirement Benefit Plans Net Periodic Benefit (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2013	Mar. 31, 2012
Pension Plans
Components of net periodic benefit cost:
Service cost	$ 844	$ 510
Interest cost	1,391	1,442
Return on plan assets	(1,884)	(1,616)
Curtailment / settlement (gain) loss	0	0
Transition costs and other	88	(16)
Net periodic benefit cost	439	320
Postretirement Benefit Plans
Components of net periodic benefit cost:
Service cost	15	18
Interest cost	46	54
Curtailment / settlement (gain) loss	0	0
Transition costs and other	9	6
Net periodic benefit cost	$ 70	$ 78