Fair Value Measures (Schedule Of Assets And Liabilities Measured At Fair Value) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds included in cash equivalents	$ 167,207	$ 106,090
Foreign currency contracts included in other current liabilities	(369)	(139)
Total financial assets and liabilities	166,838	105,951
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds included in cash equivalents	167,207	106,090
Total financial assets and liabilities	167,207	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 other current liabilities	(369)	(139)
Total financial assets and liabilities	$ (369)	$ (139)