Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balances (in shares) at Dec. 29, 2018	129,728,000
Balances at Dec. 29, 2018	$ 1,297	$ 736,274	$ (476,783)	$ (2,331)	$ 258,457
Net income for the three months ended March 28, 2020	$ 0	0	7,408	0	7,408
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes (in shares)	2,177,000
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes	$ 22	11,546	0	0	11,568
Stock-based compensation related to stock options, ESPP and RSUs	0	3,686	0	0	3,686
Translation adjustments, net of tax	0	0	0	47	47
Unrealized loss related to marketable securities, net of tax	0	0	0	42	42
Recognized gain on redemption of marketable securities, previously unrealized	$ 0	0	0	(53)	(53)
Balances (in shares) at Mar. 30, 2019	131,905,000
Balances at Mar. 30, 2019	$ 1,319	751,506	(469,375)	(2,295)	$ 281,155
Balances (in shares) at Dec. 28, 2019	133,883,000				133,883,000
Balances at Dec. 28, 2019	$ 1,339	762,213	(433,290)	(2,603)	$ 327,659
Net income for the three months ended March 28, 2020	$ 0	0	8,167	0	8,167
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes (in shares)	630,000
Common stock issued in connection with the exercise of stock options, ESPP and vested RSUs, net of shares withheld for employee taxes	$ 6	(1,490)	0	0	(1,484)
Stock-based compensation related to stock options, ESPP and RSUs	0	8,728	0	0	8,728
Translation adjustments, net of tax	$ 0	0	0	(111)	(111)
Unrealized loss related to marketable securities, net of tax					0
Recognized gain on redemption of marketable securities, previously unrealized					$ 0
Balances (in shares) at Mar. 28, 2020	134,513,000				134,513,000
Balances at Mar. 28, 2020	$ 1,345	$ 769,451	$ (425,123)	$ (2,714)	$ 342,959