Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measures (Schedule Of Assets And Liabilities Measured At Fair Value) (Details)

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Fair Value Measures (Schedule Of Assets And Liabilities Measured At Fair Value) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Foreign currency contracts included in prepaid expenses and other current assets $ 310  
Foreign currency contracts included in other current liabilities   $ (139)
Total financial assets and liabilities 157,572 105,951
Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total financial assets and liabilities 157,262 106,090
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Foreign currency contracts included in prepaid expenses and other current assets 310  
Foreign currency contracts included in other current liabilities   (139)
Total financial assets and liabilities 310 (139)
Money Market Funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 157,262 106,090
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents $ 157,262 $ 106,090