CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional Paid-in capital	Accumulated deficit	Accumulated other comprehensive loss
Beginning balances (in shares) at Dec. 30, 2017		123,895
Beginning balances at Dec. 30, 2017	$ 217,693	$ 1,239	$ 695,768	$ (477,862)	$ (1,452)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(19,201)			(19,201)
Unrealized gain related to marketable securities, net of tax	16				16
Recognized gain on redemption of marketable securities, previously unrealized	(18)				(18)
Translation adjustments, net of tax	(1,124)				(1,124)
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes (in shares)		5,380
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes	26,451	$ 54	26,397
Stock-based compensation related to stock options, ESPP and RSUs	9,908		9,908
Ending balances (in shares) at Sep. 29, 2018		129,275
Ending balances at Sep. 29, 2018	261,126	$ 1,293	732,073	(469,662)	(2,578)
Beginning balances (in shares) at Jun. 30, 2018		125,613
Beginning balances at Jun. 30, 2018	230,620	$ 1,256	707,991	(476,636)	(1,991)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,974			6,974
Unrealized gain related to marketable securities, net of tax	14				14
Recognized gain on redemption of marketable securities, previously unrealized	(17)				(17)
Translation adjustments, net of tax	(584)				(584)
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes (in shares)		3,662
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes	21,411	$ 37	21,374
Stock-based compensation related to stock options, ESPP and RSUs	2,708		2,708
Ending balances (in shares) at Sep. 29, 2018		129,275
Ending balances at Sep. 29, 2018	$ 261,126	$ 1,293	732,073	(469,662)	(2,578)
Beginning balances (in shares) at Dec. 29, 2018	129,728	129,728
Beginning balances at Dec. 29, 2018	$ 258,457	$ 1,297	736,274	(476,783)	(2,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,506			29,506
Unrealized gain related to marketable securities, net of tax	42				42
Recognized gain on redemption of marketable securities, previously unrealized	(53)				(53)
Translation adjustments, net of tax	(7)				(7)
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes (in shares)		3,774
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes	8,365	$ 38	8,327
Stock-based compensation related to stock options, ESPP and RSUs	$ 13,335		13,335
Ending balances (in shares) at Sep. 28, 2019	133,502	133,502
Ending balances at Sep. 28, 2019	$ 309,645	$ 1,335	757,936	(447,277)	(2,349)
Beginning balances (in shares) at Jun. 29, 2019		132,536
Beginning balances at Jun. 29, 2019	295,177	$ 1,325	756,924	(460,816)	(2,256)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,539			13,539
Translation adjustments, net of tax	(93)				(93)
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes (in shares)		966
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes	(4,658)	$ 10	(4,668)
Stock-based compensation related to stock options, ESPP and RSUs	$ 5,680		5,680
Ending balances (in shares) at Sep. 28, 2019	133,502	133,502
Ending balances at Sep. 28, 2019	$ 309,645	$ 1,335	$ 757,936	$ (447,277)	$ (2,349)