Marketable Securities Available-for-sale Securities - Continuous Loss Position (Details) - USD ($) $ in Thousands	Sep. 27, 2020	Dec. 29, 2019
Total short-term AFS securities
Short-term AFS securities
Fair value, less than 12 months	$ 71,155	$ 34,271
Gross unrealized losses, less than 12 months	(23)	(9)
Fair value, greater than 12 months	8,748	34,398
Gross unrealized losses, greater than 12 months	(2)	(15)
Fair value, total	79,903	68,669
Gross unrealized losses, total	(25)	(24)
Total long-term AFS securities
Long-term AFS securities
Fair value, less than 12 months	32,612	130,993
Gross unrealized losses, less than 12 months	(126)	(212)
Fair value, greater than 12 months	0	4,502
Gross unrealized losses, greater than 12 months	0	(4)
Fair value, total	32,612	135,495
Gross unrealized losses, total	(126)	(216)
Corporate debt securities
Short-term AFS securities
Fair value, less than 12 months	22,174	20,975
Gross unrealized losses, less than 12 months	(17)	(6)
Fair value, greater than 12 months	0	8,251
Gross unrealized losses, greater than 12 months	0	(3)
Fair value, total	22,174	29,226
Gross unrealized losses, total	(17)	(9)
Long-term AFS securities
Fair value, less than 12 months	10,466	35,891
Gross unrealized losses, less than 12 months	(22)	(25)
Fair value, greater than 12 months	0	4,502
Gross unrealized losses, greater than 12 months	0	(4)
Fair value, total	10,466	40,393
Gross unrealized losses, total	(22)	(29)
U.S. Treasury securities
Short-term AFS securities
Fair value, less than 12 months	43,982	13,296
Gross unrealized losses, less than 12 months	(4)	(3)
Fair value, greater than 12 months	0	11,147
Gross unrealized losses, greater than 12 months	0	(8)
Fair value, total	43,982	24,443
Gross unrealized losses, total	(4)	(11)
Long-term AFS securities
Fair value, less than 12 months		60,935
Gross unrealized losses, less than 12 months		(103)
Fair value, greater than 12 months		0
Gross unrealized losses, greater than 12 months		0
Fair value, total		60,935
Gross unrealized losses, total		(103)
U.S. governmental agency securities
Short-term AFS securities
Fair value, less than 12 months	4,999	0
Gross unrealized losses, less than 12 months	(2)	0
Fair value, greater than 12 months	8,748	15,000
Gross unrealized losses, greater than 12 months	(2)	(4)
Fair value, total	13,747	15,000
Gross unrealized losses, total	(4)	(4)
Long-term AFS securities
Fair value, less than 12 months	22,146	34,167
Gross unrealized losses, less than 12 months	(104)	(84)
Fair value, greater than 12 months	0	0
Gross unrealized losses, greater than 12 months	0	0
Fair value, total	22,146	34,167
Gross unrealized losses, total	$ (104)	$ (84)