Stockholders' Equity - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2020	Dec. 29, 2019	Dec. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 1,173,863	$ 1,042,641	$ 897,363
Income tax expense	31,125	8,179	(198)
Net current-period other comprehensive income, net of tax	84,795	22,748	(560)
Ending balance	1,328,111	1,173,863	1,042,641
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	3,438
Other comprehensive income before reclassifications, before tax	6,763
Amounts reclassified from accumulated other comprehensive loss, before tax	0
Income tax expense	1,815
Net current-period other comprehensive income, net of tax	4,948
Ending balance	8,386	3,438
Funded Status of Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(498,986)
Other comprehensive income before reclassifications, before tax	129
Amounts reclassified from accumulated other comprehensive loss, before tax	105,531
Income tax expense	28,372
Net current-period other comprehensive income, net of tax	77,288
Ending balance	(421,698)	(498,986)
Net unrealized gain on Available-for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	572
Other comprehensive income before reclassifications, before tax	3,497
Amounts reclassified from accumulated other comprehensive loss, before tax	0
Income tax expense	938
Net current-period other comprehensive income, net of tax	2,559
Ending balance	3,131	572
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(494,976)	(517,724)	(423,029)
Other comprehensive income before reclassifications, before tax	10,389
Amounts reclassified from accumulated other comprehensive loss, before tax	105,531
Income tax expense	31,125
Net current-period other comprehensive income, net of tax	84,795	22,748	(560)
Ending balance	$ (410,181)	$ (494,976)	$ (517,724)