Derivative Financial Instruments (Schedule of Company's Derivative Instruments on Other Comprehensive Income and the Consolidated Statement of Operations) (Details) - Foreign currency forward contracts - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Recognized in OCI - Effective Portion	$ 329	$ (634)
Gains (Losses) Reclassified from OCI into Income - Effective Portion	306	(1,326)
Net revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Reclassified from OCI into Income - Effective Portion	414	(1,702)
Cost of revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Reclassified from OCI into Income - Effective Portion	(2)	6
Research and development
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Reclassified from OCI into Income - Effective Portion	(26)	99
Sales and marketing
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Reclassified from OCI into Income - Effective Portion	(69)	230
General and administrative
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Reclassified from OCI into Income - Effective Portion	$ (11)	$ 41