Marketable Securities - Available for Sale (Details) - USD ($) $ in Thousands	Mar. 28, 2021	Dec. 27, 2020
Short-term AFS securities
Amortized cost, short-term AFS securities	$ 296,988	$ 308,490
Gross unrealized gains, short-term AFS securities	486	604
Gross unrealized losses, short-term AFS securities	(20)	(14)
Fair value, short-term AFS securities	297,454	309,080
Long-term AFS securities
Amortized cost, long-term AFS securities	315,243	283,143
Gross unrealized gains, long-term AFS securities	2,892	3,716
Gross unrealized losses, long-term AFS securities	(147)	(28)
Fair value, long-term AFS securities	317,988	286,831
Corporate debt securities
Short-term AFS securities
Amortized cost, short-term AFS securities	125,933	129,805
Gross unrealized gains, short-term AFS securities	417	504
Gross unrealized losses, short-term AFS securities	(19)	(8)
Fair value, short-term AFS securities	126,331	130,301
Long-term AFS securities
Amortized cost, long-term AFS securities	150,272	134,296
Gross unrealized gains, long-term AFS securities	1,125	1,643
Gross unrealized losses, long-term AFS securities	(119)	(5)
Fair value, long-term AFS securities	151,278	135,934
Certificates of deposit
Short-term AFS securities
Amortized cost, short-term AFS securities	59,083	36,525
Gross unrealized gains, short-term AFS securities	0	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	59,083	36,525
U.S. Treasury securities
Short-term AFS securities
Amortized cost, short-term AFS securities	51,225	79,467
Gross unrealized gains, short-term AFS securities	27	39
Gross unrealized losses, short-term AFS securities	(1)	(3)
Fair value, short-term AFS securities	51,251	79,503
Long-term AFS securities
Amortized cost, long-term AFS securities	101,222	95,511
Gross unrealized gains, long-term AFS securities	1,751	2,054
Gross unrealized losses, long-term AFS securities	(8)	0
Fair value, long-term AFS securities	102,965	97,565
U.S. governmental agency securities
Short-term AFS securities
Amortized cost, short-term AFS securities	39,362	25,113
Gross unrealized gains, short-term AFS securities	42	61
Gross unrealized losses, short-term AFS securities	0	(3)
Fair value, short-term AFS securities	39,404	25,171
Long-term AFS securities
Amortized cost, long-term AFS securities	51,588	48,342
Gross unrealized gains, long-term AFS securities	15	19
Gross unrealized losses, long-term AFS securities	(13)	(13)
Fair value, long-term AFS securities	51,590	48,348
Commercial paper
Short-term AFS securities
Amortized cost, short-term AFS securities	21,385	37,580
Gross unrealized gains, short-term AFS securities	0	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	21,385	37,580
Municipal securities
Long-term AFS securities
Amortized cost, long-term AFS securities	12,161	4,994
Gross unrealized gains, long-term AFS securities	1	0
Gross unrealized losses, long-term AFS securities	(7)	(10)
Fair value, long-term AFS securities	$ 12,155	$ 4,984