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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Fair Value Hierarchy for Financial Assets (Details) - USD ($)
$ in Thousands
Mar. 30, 2019
Dec. 29, 2018
Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Cash and cash equivalents $ 412,861 $ 552,490 $ 369,498
Short-term investments 180,000 $ 0  
Recurring      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 592,861    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax 0    
Available-for-sale Securities 592,861    
Cash and cash equivalents 412,861    
Short-term investments 180,000    
Recurring | Cash and Cash Equivalents      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 412,861    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax 0    
Available-for-sale Securities 412,861    
Cash and cash equivalents 412,861    
Short-term investments 0    
Recurring | Fair Value, Inputs, Level 1      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 180,000    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax 0    
Available-for-sale Securities 180,000    
Cash and cash equivalents 0    
Short-term investments 180,000    
Recurring | Fair Value, Inputs, Level 1 | Certificates of Deposit      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 180,000    
Available-for-sale Securities 180,000    
Short-term investments 180,000    
Recurring | Fair Value, Inputs, Level 2      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 0    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax 0    
Available-for-sale Securities 0    
Cash and cash equivalents 0    
Short-term investments 0    
Recurring | Fair Value, Inputs, Level 3      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 0    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax 0    
Available-for-sale Securities 0    
Cash and cash equivalents 0    
Short-term investments $ 0