Changes in Stockholders' Equity and Accumulated Other Comprehensive Loss (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 29, 2018	Sep. 30, 2017	Dec. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)			123,895	123,895
Beginning balance			$ 217,693	$ 217,693
Net loss for the nine months ended September 29, 2018	$ 6,974	$ (43,052)		(19,201)	$ (63,349)
Unrealized gain related to marketable securities, net of tax				16
Recognized gain on redemption of marketable securities, previously unrealized				(18)
Translation adjustments, net of tax				(1,124)
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of tax				26,451
Stock-based compensation related to stock options, ESPP and RSUs				$ 9,908
Accounting method transition adjustment						$ 27,401
Ending balance (in shares)	129,275			129,275
Ending balance	$ 261,126			$ 261,126
Common stock, par value per share (in dollars per share)	$ 0.01			$ 0.01		$ 0.01
Common stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	129,275		123,895	123,895
Beginning balance			$ 1,239	$ 1,239
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of tax (in shares)			5,380
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of tax				54
Ending balance (in shares)			129,275
Ending balance	$ 1,293			1,293
Additional Paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 695,768	695,768
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of tax				26,397
Stock-based compensation related to stock options, ESPP and RSUs				9,908
Ending balance	732,073			732,073
Accumulated deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(477,862)	(477,862)
Net loss for the nine months ended September 29, 2018				(19,201)
Accounting method transition adjustment						$ 27,401
Ending balance	(469,662)			(469,662)
Accumulated other comprehensive loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ (1,452)	(1,452)
Unrealized gain related to marketable securities, net of tax				16
Recognized gain on redemption of marketable securities, previously unrealized				(18)
Translation adjustments, net of tax				(1,124)
Ending balance	$ (2,578)			$ (2,578)