Supplemental Stockholders' Equity Information Reclassifications Out of Accumulated Other Comprehensive Income (Details) $ in Thousands	9 Months Ended
	Sep. 24, 2017 USD ($)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, before tax	$ 20,762
Amortization of prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, before tax	(7,274)
Amortization of actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, before tax	28,036
Total reclassifications
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, before tax	20,762
Income tax expense	8,208
Total reclassification, net of tax	$ 12,554