Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance Value at Dec. 30, 2017	$ 262,383	$ 26	$ 255,368	$ 9,113	$ (2,124)
Beginning Balance Shares at Dec. 30, 2017		24,628,722
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,056			34,056
Adjustment due to adoption of ASU 2014-09 Revenue from Contracts with Customers, net of tax	642			642
Foreign currency translation adjustments	(568)				(568)
Unrealized gain (loss) on investments, net of tax	(37)				(37)
Issuance of common stock under stock-based compensation plans, net of taxes paid	(22)	$ (2)	(20)
Issuance of common stock under stock-based compensation plans, net of taxes paid, Shares		333,833
Stock-based compensation expense	5,017		5,017
Repurchases and retirement of common stock under share repurchase plans	(22,987)		(22,987)
Repurchases and retirement of common stock under share repurchase plans, Shares		(896,187)
Ending Balance Value at Jun. 30, 2018	278,484	$ 24	237,378	43,811	(2,729)
Ending Balance Shares at Jun. 30, 2018		24,066,368
Beginning Balance Value at Mar. 31, 2018	260,727	$ 24	234,793	26,136	(226)
Beginning Balance Shares at Mar. 31, 2018		23,890,563
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,675			17,675
Foreign currency translation adjustments	(2,555)				(2,555)
Unrealized gain (loss) on investments, net of tax	52				52
Issuance of common stock under stock-based compensation plans, net of taxes paid	(94)		(94)
Issuance of common stock under stock-based compensation plans, net of taxes paid, Shares		175,805
Stock-based compensation expense	2,679		2,679
Ending Balance Value at Jun. 30, 2018	278,484	$ 24	237,378	43,811	(2,729)
Ending Balance Shares at Jun. 30, 2018		24,066,368
Beginning Balance Value at Dec. 29, 2018	$ 312,852	$ 24	247,983	67,402	(2,557)
Beginning Balance Shares at Dec. 29, 2018	24,372,193	24,372,193
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 6,903			6,903
Foreign currency translation adjustments	602				602
Unrealized gain (loss) on investments, net of tax	102				102
Issuance of common stock under stock-based compensation plans, net of taxes paid	2,207	$ 1	2,206
Issuance of common stock under stock-based compensation plans, net of taxes paid, Shares		456,191
Stock-based compensation expense	6,314		6,314
Ending Balance Value at Jun. 29, 2019	$ 328,980	$ 25	256,503	74,305	(1,853)
Ending Balance Shares at Jun. 29, 2019	24,828,384	24,828,384
Beginning Balance Value at Mar. 30, 2019	$ 320,386	$ 25	251,841	70,375	(1,855)
Beginning Balance Shares at Mar. 30, 2019		24,534,582
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,930			3,930
Foreign currency translation adjustments	(42)				(42)
Unrealized gain (loss) on investments, net of tax	44				44
Issuance of common stock under stock-based compensation plans, net of taxes paid	1,462		1,462
Issuance of common stock under stock-based compensation plans, net of taxes paid, Shares		293,802
Stock-based compensation expense	3,200		3,200
Ending Balance Value at Jun. 29, 2019	$ 328,980	$ 25	$ 256,503	$ 74,305	$ (1,853)
Ending Balance Shares at Jun. 29, 2019	24,828,384	24,828,384