Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 28, 2019
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	$ 395,597	$ 431,916
Gross Unrealized Gains	119	143
Gross Unrealized Losses	(1,183)	(78)
Debt Securities, Available-for-sale	394,533	431,981
Cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	210,370	249,952
Debt Securities, Available-for-sale	210,370	249,952
Cash equivalents [Member] \| Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	149,756	185,666
Debt Securities, Available-for-sale	149,756	185,666
Cash equivalents [Member] \| Time deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	60,614	64,286
Debt Securities, Available-for-sale	60,614	64,286
Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	99,035	85,778
Gross Unrealized Gains	69	52
Gross Unrealized Losses	(330)	(11)
Debt Securities, Available-for-sale	98,774	85,819
Short-term investments [Member] \| Time deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	14,737	2,506
Debt Securities, Available-for-sale	14,737	2,506
Short-term investments [Member] \| Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	5,000
Gross Unrealized Losses	(26)
Debt Securities, Available-for-sale	4,974
Short-term investments [Member] \| Government and corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	79,298	83,272
Gross Unrealized Gains	69	52
Gross Unrealized Losses	(304)	(11)
Debt Securities, Available-for-sale	79,063	83,313
Long-term investments [Member] \| Government and corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	86,192	96,186
Gross Unrealized Gains	50	91
Gross Unrealized Losses	(853)	(67)
Debt Securities, Available-for-sale	$ 85,389	$ 96,210

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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