Marketable Securities - Available for Sale Securities (Details) - USD ($) $ in Thousands	Dec. 29, 2019	Dec. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Net unrealized gains and losses AOCI	$ 494,976	$ 517,724
Short-term AFS securities
Amortized cost, short-term AFS securities	201,495	372,650
Gross unrealized gains, short-term AFS securities	314	1
Gross unrealized losses, short-term AFS securities	(24)	(1,350)
Fair value, short-term AFS securities	201,785	371,301
Long-term AFS securities
Amortized cost, long-term AFS securities	251,206	215,053
Gross unrealized gains, long-term AFS securities	706	52
Gross unrealized losses, long-term AFS securities	(216)	(1,547)
Fair value, long-term AFS securities	251,696	213,558
Corporate debt securities
Short-term AFS securities
Amortized cost, short-term AFS securities	98,864	140,631
Gross unrealized gains, short-term AFS securities	271	1
Gross unrealized losses, short-term AFS securities	(9)	(464)
Fair value, short-term AFS securities	99,126	140,168
Long-term AFS securities
Amortized cost, long-term AFS securities	103,149	130,612
Gross unrealized gains, long-term AFS securities	617	44
Gross unrealized losses, long-term AFS securities	(29)	(1,032)
Fair value, long-term AFS securities	103,737	129,624
U.S. Treasury securities
Short-term AFS securities
Amortized cost, short-term AFS securities	43,098	107,717
Gross unrealized gains, short-term AFS securities	8	0
Gross unrealized losses, short-term AFS securities	(11)	(232)
Fair value, short-term AFS securities	43,095	107,485
Long-term AFS securities
Amortized cost, long-term AFS securities	101,457	47,079
Gross unrealized gains, long-term AFS securities	84	5
Gross unrealized losses, long-term AFS securities	(103)	(347)
Fair value, long-term AFS securities	101,438	46,737
U.S. governmental agency securities
Short-term AFS securities
Amortized cost, short-term AFS securities	37,471	92,628
Gross unrealized gains, short-term AFS securities	35	0
Gross unrealized losses, short-term AFS securities	(4)	(654)
Fair value, short-term AFS securities	37,502	91,974
Long-term AFS securities
Amortized cost, long-term AFS securities	46,600	37,362
Gross unrealized gains, long-term AFS securities	5	3
Gross unrealized losses, long-term AFS securities	(84)	(168)
Fair value, long-term AFS securities	46,521	37,197
Commercial paper
Short-term AFS securities
Amortized cost, short-term AFS securities	12,561	8,177
Gross unrealized gains, short-term AFS securities	0	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	12,561	8,177
Certificates of deposit
Short-term AFS securities
Amortized cost, short-term AFS securities	9,501	23,497
Gross unrealized gains, short-term AFS securities	0	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	9,501	23,497
Debt Securities
Debt Securities, Available-for-sale [Line Items]
Net unrealized gains and losses AOCI	$ (800)	$ 2,800