Marketable Securities - Available for Sale (Details) - USD ($) $ in Thousands	Sep. 26, 2021	Dec. 27, 2020
Short-term AFS securities
Amortized cost, short-term AFS securities	$ 356,561	$ 308,490
Gross unrealized gains, short-term AFS securities	1,269	604
Gross unrealized losses, short-term AFS securities	(16)	(14)
Fair value, short-term AFS securities	357,814	309,080
Long-term AFS securities
Amortized cost, long-term AFS securities	360,313	283,143
Gross unrealized gains, long-term AFS securities	799	3,716
Gross unrealized losses, long-term AFS securities	(391)	(28)
Fair value, long-term AFS securities	360,721	286,831
U.S. Treasury securities
Short-term AFS securities
Amortized cost, short-term AFS securities	108,696	79,467
Gross unrealized gains, short-term AFS securities	898	39
Gross unrealized losses, short-term AFS securities	(2)	(3)
Fair value, short-term AFS securities	109,592	79,503
Long-term AFS securities
Amortized cost, long-term AFS securities	71,722	95,511
Gross unrealized gains, long-term AFS securities	200	2,054
Gross unrealized losses, long-term AFS securities	(61)	0
Fair value, long-term AFS securities	71,861	97,565
Certificates of deposit
Short-term AFS securities
Amortized cost, short-term AFS securities	109,253	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	109,253	36,525
Corporate debt securities
Short-term AFS securities
Amortized cost, short-term AFS securities	100,627	129,805
Gross unrealized gains, short-term AFS securities	361	504
Gross unrealized losses, short-term AFS securities	(14)	(8)
Fair value, short-term AFS securities	100,974	130,301
Long-term AFS securities
Amortized cost, long-term AFS securities	233,971	134,296
Gross unrealized gains, long-term AFS securities	594	1,643
Gross unrealized losses, long-term AFS securities	(274)	(5)
Fair value, long-term AFS securities	234,291	135,934
U.S. governmental agency securities
Short-term AFS securities
Amortized cost, short-term AFS securities	19,964	25,113
Gross unrealized gains, short-term AFS securities	10	61
Gross unrealized losses, short-term AFS securities	0	(3)
Fair value, short-term AFS securities	19,974	25,171
Long-term AFS securities
Amortized cost, long-term AFS securities	42,497	48,342
Gross unrealized gains, long-term AFS securities	0	19
Gross unrealized losses, long-term AFS securities	(43)	(13)
Fair value, long-term AFS securities	42,454	48,348
Commercial paper
Short-term AFS securities
Amortized cost, short-term AFS securities	18,021	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	18,021	37,580
Municipal securities
Long-term AFS securities
Amortized cost, long-term AFS securities	12,123	4,994
Gross unrealized gains, long-term AFS securities	5	0
Gross unrealized losses, long-term AFS securities	(13)	(10)
Fair value, long-term AFS securities	$ 12,115	$ 4,984