Investments (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 29, 2018
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 436,437	$ 578,512
Gross Unrealized Gains	144	1
Gross Unrealized Losses	(93)	(1,104)
Debt Securities, Available-for-sale	436,488	577,409
Cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	227,489	157,932
Debt Securities, Available-for-sale	227,489	157,932
Cash equivalents [Member] \| Money market funds [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	140,504	76,471
Debt Securities, Available-for-sale	140,504	76,471
Cash equivalents [Member] \| Time deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	59,585	71,461
Debt Securities, Available-for-sale	59,585	71,461
Cash equivalents [Member] \| Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	27,400	10,000
Debt Securities, Available-for-sale	27,400	10,000
Short-term investments [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	127,517	402,333
Gross Unrealized Gains	66	1
Gross Unrealized Losses	(39)	(1,049)
Debt Securities, Available-for-sale	127,544	401,285
Short-term investments [Member] \| Time deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	5,690	31,947
Debt Securities, Available-for-sale	5,690	31,947
Short-term investments [Member] \| Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	17,750	75,445
Gross Unrealized Gains	13
Gross Unrealized Losses	(10)	(91)
Debt Securities, Available-for-sale	17,753	75,354
Short-term investments [Member] \| Government and corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	104,077	294,941
Gross Unrealized Gains	53	1
Gross Unrealized Losses	(29)	(958)
Debt Securities, Available-for-sale	104,101	293,984
Long-term investments [Member] \| Government and corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	81,431	18,247
Gross Unrealized Gains	78
Gross Unrealized Losses	(54)	(55)
Debt Securities, Available-for-sale	$ 81,455	$ 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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