Marketable Securities - Available for Sale (Details) - USD ($) $ in Thousands	Jun. 27, 2021	Dec. 27, 2020
Short-term AFS securities
Amortized cost, short-term AFS securities	$ 337,411	$ 308,490
Gross unrealized gains, short-term AFS securities	1,059	604
Gross unrealized losses, short-term AFS securities	(15)	(14)
Fair value, short-term AFS securities	338,455	309,080
Long-term AFS securities
Amortized cost, long-term AFS securities	285,877	283,143
Gross unrealized gains, long-term AFS securities	1,599	3,716
Gross unrealized losses, long-term AFS securities	(211)	(28)
Fair value, long-term AFS securities	287,265	286,831
Corporate debt securities
Short-term AFS securities
Amortized cost, short-term AFS securities	110,415	129,805
Gross unrealized gains, short-term AFS securities	496	504
Gross unrealized losses, short-term AFS securities	(12)	(8)
Fair value, short-term AFS securities	110,899	130,301
Long-term AFS securities
Amortized cost, long-term AFS securities	161,767	134,296
Gross unrealized gains, long-term AFS securities	725	1,643
Gross unrealized losses, long-term AFS securities	(123)	(5)
Fair value, long-term AFS securities	162,369	135,934
Certificates of deposit
Short-term AFS securities
Amortized cost, short-term AFS securities	105,954	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	105,954	36,525
U.S. Treasury securities
Short-term AFS securities
Amortized cost, short-term AFS securities	74,984	79,467
Gross unrealized gains, short-term AFS securities	547	39
Gross unrealized losses, short-term AFS securities	(3)	(3)
Fair value, short-term AFS securities	75,528	79,503
Long-term AFS securities
Amortized cost, long-term AFS securities	60,377	95,511
Gross unrealized gains, long-term AFS securities	861	2,054
Gross unrealized losses, long-term AFS securities	(15)	0
Fair value, long-term AFS securities	61,223	97,565
U.S. governmental agency securities
Short-term AFS securities
Amortized cost, short-term AFS securities	26,137	25,113
Gross unrealized gains, short-term AFS securities	16	61
Gross unrealized losses, short-term AFS securities	0	(3)
Fair value, short-term AFS securities	26,153	25,171
Long-term AFS securities
Amortized cost, long-term AFS securities	51,591	48,342
Gross unrealized gains, long-term AFS securities	6	19
Gross unrealized losses, long-term AFS securities	(67)	(13)
Fair value, long-term AFS securities	51,530	48,348
Commercial paper
Short-term AFS securities
Amortized cost, short-term AFS securities	19,921	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	19,921	37,580
Municipal securities
Long-term AFS securities
Amortized cost, long-term AFS securities	12,142	4,994
Gross unrealized gains, long-term AFS securities	7	0
Gross unrealized losses, long-term AFS securities	(6)	(10)
Fair value, long-term AFS securities	$ 12,143	$ 4,984