Derivative Financial Instruments (Schedule of Effects and Locations of Gains or Losses Recognized in Income) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Net revenue		$ 400,586	$ 355,483	$ 1,112,379	$ 1,009,863
Cost of revenue		276,394	252,388	774,510	717,900
Research and development		35,253	23,127	95,571	69,167
Sales and marketing		49,005	40,311	139,646	115,001
General and administrative		23,268	14,229	60,354	40,373
Amount Reclassified from AOCI | Foreign currency forward contracts | Designated as Hedging Instrument | Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Net revenue	[1]	1,031	(4,401)	246	(3,374)
Cost of revenue	[1]	(7)	19	(8)	5
Research and development	[1]	2	84	88	10
Sales and marketing	[1]	(138)	629	(65)	380
General and administrative	[1]	$ (41)	$ 109	$ (50)	$ 67

[1] Refer to Note 11, Stockholders' Equity, which summarizes the accumulated other comprehensive income activity related to derivatives.