Supplemental Equity Information - Reclassifications out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 28, 2015	Jun. 30, 2016	Jun. 28, 2015
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	$ 80	$ (618)	$ 130	$ (1,236)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	2,342	15,713	4,192	31,408
Accumulated Defined Benefit Plans Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	2,422	15,095	4,322	30,172
Income tax effect	(942)	(5,435)	(1,680)	(10,867)
Total reclassifications, net of tax	$ 1,480	$ 9,660	$ 2,642	$ 19,305