Marketable Securities - Continuous Loss Position (Details) - USD ($)	12 Months Ended
	Dec. 29, 2019	Dec. 30, 2018
Long-term AFS securities
Other than temporary impairment, loss	$ 0
Minimum | Short-term Marketable Securities
Long-term AFS securities
Remaining maturities on short-term and long-term marketable securities	1 month
Minimum | Long-term Marketable Securities
Long-term AFS securities
Remaining maturities on short-term and long-term marketable securities	13 months
Maximum | Short-term Marketable Securities
Long-term AFS securities
Remaining maturities on short-term and long-term marketable securities		12 months
Maximum | Long-term Marketable Securities
Long-term AFS securities
Remaining maturities on short-term and long-term marketable securities		35 months
Corporate debt securities
Short-term AFS securities
Fair value, less than 12 months, short-term AFS securities	$ 20,975,000	$ 76,886,000
Gross unrealized losses, less than 12 months, short-term AFS securities	(6,000)	(115,000)
Fair value, 12 months or greater, short-term AFS securities	8,251,000	61,459,000
Gross unrealized losses, 12 months or greater, short-term AFS securities	(3,000)	(349,000)
Fair value, short-term AFS securities	29,226,000	138,345,000
Gross unrealized losses, short-term AFS securities	(9,000)	(464,000)
Long-term AFS securities
Fair value, less than 12 months, long-term AFS securities	35,891,000	81,655,000
Gross unrealized losses, less than 12 months, long-term AFS securities	(25,000)	(570,000)
Fair value, 12 months or greater, long-term AFS securities	4,502,000	27,265,000
Gross unrealized losses, 12 months or greater, long-term AFS securities	(4,000)	(462,000)
Fair value, long-term AFS securities	40,393,000	108,920,000
Gross unrealized losses, long-term AFS securities	(29,000)	(1,032,000)
U.S. Treasury securities
Short-term AFS securities
Fair value, less than 12 months, short-term AFS securities	13,296,000	70,830,000
Gross unrealized losses, less than 12 months, short-term AFS securities	(3,000)	(31,000)
Fair value, 12 months or greater, short-term AFS securities	11,147,000	28,207,000
Gross unrealized losses, 12 months or greater, short-term AFS securities	(8,000)	(201,000)
Fair value, short-term AFS securities	24,443,000	99,037,000
Gross unrealized losses, short-term AFS securities	(11,000)	(232,000)
Long-term AFS securities
Fair value, less than 12 months, long-term AFS securities	60,935,000	21,579,000
Gross unrealized losses, less than 12 months, long-term AFS securities	(103,000)	(36,000)
Fair value, 12 months or greater, long-term AFS securities	0	11,868,000
Gross unrealized losses, 12 months or greater, long-term AFS securities	0	(132,000)
Fair value, long-term AFS securities	60,935,000	33,447,000
Gross unrealized losses, long-term AFS securities	(103,000)	(168,000)
U.S. governmental agency securities
Short-term AFS securities
Fair value, less than 12 months, short-term AFS securities	0	11,664,000
Gross unrealized losses, less than 12 months, short-term AFS securities	0	(4,000)
Fair value, 12 months or greater, short-term AFS securities	15,000,000	80,311,000
Gross unrealized losses, 12 months or greater, short-term AFS securities	(4,000)	(650,000)
Fair value, short-term AFS securities	15,000,000	91,975,000
Gross unrealized losses, short-term AFS securities	(4,000)	(654,000)
Long-term AFS securities
Fair value, less than 12 months, long-term AFS securities	34,167,000	20,479,000
Gross unrealized losses, less than 12 months, long-term AFS securities	(84,000)	(29,000)
Fair value, 12 months or greater, long-term AFS securities	0	23,762,000
Gross unrealized losses, 12 months or greater, long-term AFS securities	0	(318,000)
Fair value, long-term AFS securities	34,167,000	44,241,000
Gross unrealized losses, long-term AFS securities	(84,000)	(347,000)
Short-term Available-for Sale Securities [Member]
Short-term AFS securities
Fair value, less than 12 months, short-term AFS securities	34,271,000	159,380,000
Gross unrealized losses, less than 12 months, short-term AFS securities	(9,000)	(150,000)
Fair value, 12 months or greater, short-term AFS securities	34,398,000	169,977,000
Gross unrealized losses, 12 months or greater, short-term AFS securities	(15,000)	(1,200,000)
Fair value, short-term AFS securities	68,669,000	329,357,000
Gross unrealized losses, short-term AFS securities	(24,000)	(1,350,000)
Long-term AFS securities [Member]
Long-term AFS securities
Fair value, less than 12 months, long-term AFS securities	130,993,000	123,713,000
Gross unrealized losses, less than 12 months, long-term AFS securities	(212,000)	(635,000)
Fair value, 12 months or greater, long-term AFS securities	4,502,000	62,895,000
Gross unrealized losses, 12 months or greater, long-term AFS securities	(4,000)	(912,000)
Fair value, long-term AFS securities	135,495,000	186,608,000
Gross unrealized losses, long-term AFS securities	$ (216,000)	$ (1,547,000)