Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 28, 2019
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	$ 287,326	$ 431,916
Gross Unrealized Gains	957	143
Gross Unrealized Losses	(24)	(78)
Debt Securities, Available-for-sale	288,259	431,981
Cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	94,810	249,952
Debt Securities, Available-for-sale	94,810	249,952
Cash equivalents [Member] | Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	36,403	185,666
Debt Securities, Available-for-sale	36,403	185,666
Cash equivalents [Member] | Time deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	58,407	64,286
Debt Securities, Available-for-sale	58,407	64,286
Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	130,043	85,778
Gross Unrealized Gains	572	52
Gross Unrealized Losses	(14)	(11)
Debt Securities, Available-for-sale	130,601	85,819
Short-term investments [Member] | Time deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	21,445	2,506
Debt Securities, Available-for-sale	21,445	2,506
Short-term investments [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	10,000
Gross Unrealized Gains	12
Gross Unrealized Losses	(7)
Debt Securities, Available-for-sale	10,005
Short-term investments [Member] | Government and corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	98,598	83,272
Gross Unrealized Gains	560	52
Gross Unrealized Losses	(7)	(11)
Debt Securities, Available-for-sale	99,151	83,313
Long-term investments [Member] | Government and corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	62,473	96,186
Gross Unrealized Gains	385	91
Gross Unrealized Losses	(10)	(67)
Debt Securities, Available-for-sale	$ 62,848	$ 96,210