Marketable Securities - Available for Sale Securities (Details) - USD ($) $ in Thousands	Dec. 27, 2020	Dec. 29, 2019
Debt Securities, Available-for-sale [Line Items]
Net unrealized gain (loss) in AOCI	$ (410,181)	$ (494,976)
Short-term AFS securities
Amortized cost, short-term AFS securities	308,490	201,495
Gross unrealized gains, short-term AFS securities	604	314
Gross unrealized losses, short-term AFS securities	(14)	(24)
Fair value, short-term AFS securities	309,080	201,785
Long-term AFS securities
Amortized cost, long-term AFS securities	283,143	251,206
Gross unrealized gains, long-term AFS securities	3,716	706
Gross unrealized losses, long-term AFS securities	(28)	(216)
Fair value, long-term AFS securities	286,831	251,696
Corporate debt securities
Short-term AFS securities
Amortized cost, short-term AFS securities	129,805	98,864
Gross unrealized gains, short-term AFS securities	504	271
Gross unrealized losses, short-term AFS securities	(8)	(9)
Fair value, short-term AFS securities	130,301	99,126
Long-term AFS securities
Amortized cost, long-term AFS securities	134,296	103,149
Gross unrealized gains, long-term AFS securities	1,643	617
Gross unrealized losses, long-term AFS securities	(5)	(29)
Fair value, long-term AFS securities	135,934	103,737
U.S. Treasury securities
Short-term AFS securities
Amortized cost, short-term AFS securities	79,467	43,098
Gross unrealized gains, short-term AFS securities	39	8
Gross unrealized losses, short-term AFS securities	(3)	(11)
Fair value, short-term AFS securities	79,503	43,095
Long-term AFS securities
Amortized cost, long-term AFS securities	95,511	101,457
Gross unrealized gains, long-term AFS securities	2,054	84
Gross unrealized losses, long-term AFS securities	0	(103)
Fair value, long-term AFS securities	97,565	101,438
Commercial paper
Short-term AFS securities
Amortized cost, short-term AFS securities	37,580	12,561
Gross unrealized gains, short-term AFS securities	0	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	37,580	12,561
Certificates of deposit
Short-term AFS securities
Amortized cost, short-term AFS securities	36,525	9,501
Gross unrealized gains, short-term AFS securities	0	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	36,525	9,501
U.S. governmental agency securities
Short-term AFS securities
Amortized cost, short-term AFS securities	25,113	37,471
Gross unrealized gains, short-term AFS securities	61	35
Gross unrealized losses, short-term AFS securities	(3)	(4)
Fair value, short-term AFS securities	25,171	37,502
Long-term AFS securities
Amortized cost, long-term AFS securities	48,342	46,600
Gross unrealized gains, long-term AFS securities	19	5
Gross unrealized losses, long-term AFS securities	(13)	(84)
Fair value, long-term AFS securities	48,348	46,521
Municipal securities
Long-term AFS securities
Amortized cost, long-term AFS securities	4,994
Gross unrealized gains, long-term AFS securities	0
Gross unrealized losses, long-term AFS securities	(10)
Fair value, long-term AFS securities	4,984
Debt Securities
Debt Securities, Available-for-sale [Line Items]
Net unrealized gain (loss) in AOCI	$ 4,300	$ 800