Fair Value of Financial Instruments - Contractual maturities of investments (Details) - USD ($) $ in Thousands	Apr. 03, 2021	Jan. 02, 2021
Cost
Due in one year or less, Cost	$ 270,863
Due after one year through ten years, Cost	151,369
Due after ten years, Cost	18,800
Total Cost	441,032
Fair Value
Due in one year or less, Fair Value	271,720
Due after one year through ten years, Fair Value	151,669
Due after ten years, Fair Value	18,062
Total Fair Value	441,451
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	66,261	$ 62,055
Fair value of available-for-sale securities, continuous loss position for twelve months or greater	5,262	5,340
Total fair value of available-for-sale securities, continuous loss position	71,523	67,395
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(62)	(79)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(738)	(660)
Available-for-sale securities, total gross unrealized losses	(800)	(739)
Government debt securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	6,719	10,146
Total fair value of available-for-sale securities, continuous loss position	6,719	10,146
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(6)	(5)
Available-for-sale securities, total gross unrealized losses	(6)	(5)
Corporate debt securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	59,542	51,909
Total fair value of available-for-sale securities, continuous loss position	59,542	51,909
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(56)	(74)
Available-for-sale securities, total gross unrealized losses	(56)	(74)
Auction rate securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for twelve months or greater	5,262	5,340
Total fair value of available-for-sale securities, continuous loss position	5,262	5,340
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(738)	(660)
Available-for-sale securities, total gross unrealized losses	$ (738)	$ (660)