Supplemental Stockholders' Equity Information - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	$ 1,231,031	$ 1,085,203	$ 1,173,863	$ 1,042,641
Income tax expense	2,192	489	6,955	3,903
Other comprehensive income, net of tax	6,038	1,529	19,058	11,269
Balance, end of period	1,257,254	1,097,766	1,257,254	1,097,766
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			3,438
Other comprehensive (loss)/income before reclassifications, before tax			3,095
Amounts reclassified from accumulated other comprehensive loss, before tax			0
Income tax expense			823
Other comprehensive income, net of tax			2,272
Balance, end of period	5,710		5,710
Funded Status of Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			(498,986)
Other comprehensive (loss)/income before reclassifications, before tax			0
Amounts reclassified from accumulated other comprehensive loss, before tax			18,982
Income tax expense			5,083
Other comprehensive income, net of tax			13,899
Balance, end of period	(485,087)		(485,087)
Net Unrealized Gain on Available-For-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			572
Other comprehensive (loss)/income before reclassifications, before tax			3,936
Amounts reclassified from accumulated other comprehensive loss, before tax			0
Income tax expense			1,049
Other comprehensive income, net of tax			2,887
Balance, end of period	3,459		3,459
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(481,956)	(507,984)	(494,976)	(517,724)
Other comprehensive (loss)/income before reclassifications, before tax			7,031
Amounts reclassified from accumulated other comprehensive loss, before tax			18,982
Income tax expense			6,955
Other comprehensive income, net of tax	6,038	1,529	19,058	11,269
Balance, end of period	$ (475,918)	$ (506,455)	$ (475,918)	$ (506,455)