Marketable Securities - Available-for-sale Securities - Continuous Loss Position (Details) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 30, 2018
Total short-term AFS securities
Short-term AFS securities
Fair value, less than 12 months	$ 32,539	$ 159,380
Gross unrealized losses, less than 12 months	(10)	(150)
Fair value, greater than 12 months	83,276	169,977
Gross unrealized losses, greater than 12 months	(90)	(1,200)
Fair value, total	115,815	329,357
Gross unrealized losses, total	(100)	(1,350)
Total long-term AFS securities
Long-term AFS securities
Fair value, less than 12 months	88,693	123,713
Gross unrealized losses, less than 12 months	(132)	(635)
Fair value, greater than 12 months	8,004	62,895
Gross unrealized losses, greater than 12 months	(7)	(912)
Fair value, total	96,697	186,608
Gross unrealized losses, total	(139)	(1,547)
US Treasury Securities
Short-term AFS securities
Fair value, less than 12 months	14,863	70,830
Gross unrealized losses, less than 12 months	(7)	(31)
Fair value, greater than 12 months	23,113	28,207
Gross unrealized losses, greater than 12 months	(40)	(201)
Fair value, total	37,976	99,037
Gross unrealized losses, total	(47)	(232)
Long-term AFS securities
Fair value, less than 12 months	35,727	21,579
Gross unrealized losses, less than 12 months	(67)	(36)
Fair value, greater than 12 months	0	11,868
Gross unrealized losses, greater than 12 months	0	(132)
Fair value, total	35,727	33,447
Gross unrealized losses, total	(67)	(168)
Corporate Debt Securities
Short-term AFS securities
Fair value, less than 12 months	12,678	76,886
Gross unrealized losses, less than 12 months	(3)	(115)
Fair value, greater than 12 months	36,975	61,459
Gross unrealized losses, greater than 12 months	(33)	(349)
Fair value, total	49,653	138,345
Gross unrealized losses, total	(36)	(464)
Long-term AFS securities
Fair value, less than 12 months	11,008	81,655
Gross unrealized losses, less than 12 months	(15)	(570)
Fair value, greater than 12 months	8,004	27,265
Gross unrealized losses, greater than 12 months	(7)	(462)
Fair value, total	19,012	108,920
Gross unrealized losses, total	(22)	(1,032)
U.S. governmental agency securities
Short-term AFS securities
Fair value, less than 12 months	4,998	11,664
Gross unrealized losses, less than 12 months	0	(4)
Fair value, greater than 12 months	23,188	80,311
Gross unrealized losses, greater than 12 months	(17)	(650)
Fair value, total	28,186	91,975
Gross unrealized losses, total	(17)	(654)
Long-term AFS securities
Fair value, less than 12 months	41,958	20,479
Gross unrealized losses, less than 12 months	(50)	(29)
Fair value, greater than 12 months	0	23,762
Gross unrealized losses, greater than 12 months	0	(318)
Fair value, total	41,958	44,241
Gross unrealized losses, total	$ (50)	$ (347)