Pension and Postretirement Benefit Plans Net Periodic Benefit (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Pension Plans
Components of net periodic benefit cost:
Service cost	$ 835	$ 504	$ 1,679	$ 1,014
Interest cost	1,379	1,429	2,770	2,871
Return on plan assets	(1,864)	(1,602)	(3,748)	(3,218)
Curtailment / settlement (gain) loss	0	233	0	233
Transition costs and other	87	(15)	175	(31)
Net periodic benefit cost	437	549	876	869
Postretirement Benefit Plans
Components of net periodic benefit cost:
Service cost	15	17	30	35
Interest cost	46	54	92	108
Curtailment / settlement (gain) loss	0	15	0	15
Transition costs and other	9	6	18	12
Net periodic benefit cost	$ 70	$ 92	$ 140	$ 170