Pension and Postretirement Benefit Plans Net Periodic Benefit (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 28, 2014	Jun. 30, 2015	Jun. 28, 2014	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year			$ 3,500
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	$ 0	$ 0	0	$ 0
Curtailment / settlement (gain) loss	0	0	0	0
Transition costs and other	89	1	180	2
Accumulated Other Comprehensive Income (Loss), Net of Tax	(73,615)		(73,615)		$ (59,164)
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,031	874	2,032	1,747
Interest cost	2,005	2,463	3,980	4,921
Expected return on plan assets	(2,733)	(3,122)	(5,419)	(6,240)
Curtailment / settlement (gain) loss	0	0	0	0
Defined Benefit Plan, Actuarial Gain (Loss)	99	(4)	197	(8)
Transition costs and other	(11)	0	(20)	0
Net periodic benefit cost	391	211	770
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	9	4	18
Interest cost	47	94	91	187
Curtailment / settlement (gain) loss	0	0	0	0
Defined Benefit Plan, Actuarial Gain (Loss)	1	5	3	10
Transition costs and other	0	0	0	0
Net periodic benefit cost	50	$ 108
United States Postretirement Benefit Plan of US Entity [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			98	215
United States Pension Plan of US Entity [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost				$ 420
Maximum
Defined Benefit Plan Disclosure [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (73,615)		$ (73,615)