Investments (Details) - USD ($) $ in Thousands	Dec. 28, 2019	Dec. 29, 2018
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 431,916	$ 578,512
Gross Unrealized Gains	143	1
Gross Unrealized Losses	(78)	(1,104)
Debt Securities, Available-for-sale	431,981	577,409
Cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	249,952	157,932
Debt Securities, Available-for-sale	249,952	157,932
Cash equivalents [Member] \| Money market funds [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	185,666	76,471
Debt Securities, Available-for-sale	185,666	76,471
Cash equivalents [Member] \| Time deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	64,286	71,461
Debt Securities, Available-for-sale	64,286	71,461
Cash equivalents [Member] \| Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		10,000
Debt Securities, Available-for-sale		10,000
Short-term investments [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	85,778	402,333
Gross Unrealized Gains	52	1
Gross Unrealized Losses	(11)	(1,049)
Debt Securities, Available-for-sale	85,819	401,285
Short-term investments [Member] \| Time deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	2,506	31,947
Debt Securities, Available-for-sale	2,506	31,947
Short-term investments [Member] \| Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		75,445
Gross Unrealized Losses		(91)
Debt Securities, Available-for-sale		75,354
Short-term investments [Member] \| Government and corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	83,272	294,941
Gross Unrealized Gains	52	1
Gross Unrealized Losses	(11)	(958)
Debt Securities, Available-for-sale	83,313	293,984
Long-term investments [Member] \| Government and corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	96,186	18,247
Gross Unrealized Gains	91
Gross Unrealized Losses	(67)	(55)
Debt Securities, Available-for-sale	$ 96,210	$ 18,192

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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