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Cash and Investments - Investments by Security Type (Details) - USD ($)
$ in Thousands
Mar. 30, 2018
Dec. 29, 2017
Investment [Line Items]    
Amortized Cost $ 505,159 $ 440,756
Gross Unrealized Gains 13 18
Gross Unrealized Losses (900) (364)
Fair Value 504,272 440,410
Money market funds    
Investment [Line Items]    
Amortized Cost 55,241 45,478
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Fair Value 55,241 45,478
Commercial paper    
Investment [Line Items]    
Amortized Cost 237,067 199,647
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Fair Value 237,067 199,647
Corporate bonds    
Investment [Line Items]    
Amortized Cost 191,361 179,336
Gross Unrealized Gains 13 18
Gross Unrealized Losses (843) (332)
Fair Value 190,531 179,022
U.S. Treasury and government sponsored enterprises    
Investment [Line Items]    
Amortized Cost 21,490 16,295
Gross Unrealized Gains 0 0
Gross Unrealized Losses (57) (32)
Fair Value $ 21,433 $ 16,263