Marketable Securities - Available-for-sale Securities - Continuous Loss Position (Details) - USD ($) $ in Thousands	Jun. 28, 2020	Dec. 29, 2019
Total short-term AFS securities
Short-term AFS securities
Fair value, less than 12 months	$ 47,216	$ 34,271
Gross unrealized losses, less than 12 months	(15)	(9)
Fair value, greater than 12 months	0	34,398
Gross unrealized losses, greater than 12 months	0	(15)
Fair value, total	47,216	68,669
Gross unrealized losses, total	(15)	(24)
Total long-term AFS securities
Long-term AFS securities
Fair value, less than 12 months	26,289	130,993
Gross unrealized losses, less than 12 months	(31)	(212)
Fair value, greater than 12 months	0	4,502
Gross unrealized losses, greater than 12 months	0	(4)
Fair value, total	26,289	135,495
Gross unrealized losses, total	(31)	(216)
Corporate debt securities
Short-term AFS securities
Fair value, less than 12 months	22,721	20,975
Gross unrealized losses, less than 12 months	(13)	(6)
Fair value, greater than 12 months	0	8,251
Gross unrealized losses, greater than 12 months	0	(3)
Fair value, total	22,721	29,226
Gross unrealized losses, total	(13)	(9)
Long-term AFS securities
Fair value, less than 12 months	17,542	35,891
Gross unrealized losses, less than 12 months	(28)	(25)
Fair value, greater than 12 months	0	4,502
Gross unrealized losses, greater than 12 months	0	(4)
Fair value, total	17,542	40,393
Gross unrealized losses, total	(28)	(29)
US Treasury Securities
Short-term AFS securities
Fair value, less than 12 months	14,496	13,296
Gross unrealized losses, less than 12 months	(1)	(3)
Fair value, greater than 12 months	0	11,147
Gross unrealized losses, greater than 12 months	0	(8)
Fair value, total	14,496	24,443
Gross unrealized losses, total	(1)	(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	9,999	0
Gross unrealized losses, less than 12 months	(1)	0
Fair value, greater than 12 months	0	15,000
Gross unrealized losses, greater than 12 months	0	(4)
Fair value, total	9,999	15,000
Gross unrealized losses, total	(1)	(4)
Long-term AFS securities
Fair value, less than 12 months	8,747	34,167
Gross unrealized losses, less than 12 months	(3)	(84)
Fair value, greater than 12 months	0	0
Gross unrealized losses, greater than 12 months	0	0
Fair value, total	8,747	34,167
Gross unrealized losses, total	$ (3)	$ (84)