Changes in Stockholders' Equity and Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Dec. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 217,693
Net loss for the three months ended March 31, 2018	(5,952)	$ (7,275)
Unrealized loss related to marketable securities, net of tax	(7)
Recognized loss on redemption of marketable securities, previously unrealized	(1)
Translation adjustments, net of tax	589
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of tax	1,149
Stock-based compensation related to stock options, ESPP and RSUs	4,800
Accounting method transition adjustment			$ 27,401
Ending balance	245,672
Common stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,239
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of tax	4
Ending balance	1,243
Additional Paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	695,768
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of tax	1,145
Stock-based compensation related to stock options, ESPP and RSUs	4,800
Ending balance	701,713
Accumulated deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(477,862)
Net loss for the three months ended March 31, 2018	(5,952)
Accounting method transition adjustment			$ 27,401
Ending balance	(456,413)
Accumulated other comprehensive loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,452)
Unrealized loss related to marketable securities, net of tax	(7)
Recognized loss on redemption of marketable securities, previously unrealized	(1)
Translation adjustments, net of tax	589
Ending balance	$ (871)