Supplemental Stockholders' Equity Information - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	$ 1,085,203	$ 979,691	$ 1,042,641	$ 897,363
Income tax (benefit)/expense	489	2,031	3,903	5,535
Other comprehensive income, net of tax	1,529	5,725	11,269	15,608
Balance, end of period	1,097,766	1,006,671	1,097,766	1,006,671
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			4,677
Other comprehensive (loss)/income before reclassifications, before tax			(3,286)
Amounts reclassified from accumulated other comprehensive loss, before tax			0
Income tax (benefit)/expense			(863)
Other comprehensive income, net of tax			(2,423)
Balance, end of period	2,254		2,254
Funded Status of Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			(520,308)
Other comprehensive (loss)/income before reclassifications, before tax			0
Amounts reclassified from accumulated other comprehensive loss, before tax			14,685
Income tax (benefit)/expense			3,780
Other comprehensive income, net of tax			10,905
Balance, end of period	(509,403)		(509,403)
Net unrealized Loss on available-for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			(2,093)
Other comprehensive (loss)/income before reclassifications, before tax			3,773
Amounts reclassified from accumulated other comprehensive loss, before tax			0
Income tax (benefit)/expense			986
Other comprehensive income, net of tax			2,787
Balance, end of period	694		694
Parent
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	1,083,343	979,606	1,040,781	897,279
Other comprehensive (loss)/income before reclassifications, before tax			487
Amounts reclassified from accumulated other comprehensive loss, before tax			14,685
Income tax (benefit)/expense			3,903
Other comprehensive income, net of tax	1,529	5,725	11,269	15,608
Balance, end of period	1,095,906	1,006,588	1,095,906	1,006,588
Accumulated Other Comprehensive Loss, Net of Income Taxes
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(507,984)	(507,281)	(517,724)	(423,029)
Other comprehensive income, net of tax	1,529	5,725	11,269	15,608
Balance, end of period	$ (506,455)	$ (501,556)	$ (506,455)	$ (501,556)