Supplemental Stockholders' Equity Information -Reclassifications Out of Accumulated Other Comprehensive Income (Details) $ in Thousands	6 Months Ended
	Jul. 01, 2018 USD ($)
Amortization of prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, before tax	$ (4,154)
Amortization of actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, before tax	18,398
Total reclassifications
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, before tax	14,244
Income tax expense	3,727
Total reclassification, net of tax	$ 10,517