Fair Value of Financial Instruments - Available-for-sale investments (Details) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019
Cost
Due in one year or less, Cost	$ 380,069
Due after one year through ten years, Cost	202,363
Due after ten years, Cost	38,780
Total Cost	621,212
Fair Value
Due in one year or less, Fair Value	381,219
Due after one year through ten years, Fair Value	203,484
Due after ten years, Fair Value	38,120
Total Fair Value	622,823
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	62,055	$ 80,063
Fair value of available-for-sale securities, continuous loss position for twelve months or greater	5,340	12,850
Total fair value of available-for-sale securities, continuous loss position	67,395	92,913
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(79)	(100)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(660)	(360)
Available-for-sale securities, total gross unrealized losses	(739)	(460)
Government debt securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	10,146	11,947
Fair value of available-for-sale securities, continuous loss position for twelve months or greater		7,183
Total fair value of available-for-sale securities, continuous loss position	10,146	19,130
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(5)	(19)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses		(7)
Available-for-sale securities, total gross unrealized losses	(5)	(26)
Corporate debt securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	51,909	68,116
Fair value of available-for-sale securities, continuous loss position for twelve months or greater		20
Total fair value of available-for-sale securities, continuous loss position	51,909	68,136
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(74)	(81)
Available-for-sale securities, total gross unrealized losses	(74)	(81)
Auction rate securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for twelve months or greater	5,340	5,647
Total fair value of available-for-sale securities, continuous loss position	5,340	5,647
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(660)	(353)
Available-for-sale securities, total gross unrealized losses	$ (660)	$ (353)