Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Net revenues:
Total net revenues	$ 76,590	$ 56,675	$ 247,507	$ 180,416
Costs of net revenues:
Amortization of intangible assets	35	52	105	156
Total costs of net revenues	32,956	26,015	105,451	87,688
Gross profit	43,634	30,660	142,056	92,728
Operating expenses:
Research and development	12,717	8,825	35,410	26,658
Selling	8,902	7,553	28,077	22,730
General and administrative	7,744	6,798	22,950	19,696
Total operating expenses	29,363	23,176	86,437	69,084
Income from operations	14,271	7,484	55,619	23,644
Other income (expense):
Interest income	4	2	8	6
Interest expense	(108)	(25)	(253)	(84)
Other income, net	322	59	508	330
Total other income, net	218	36	263	252
Income before income taxes	14,489	7,520	55,882	23,896
Provision for income taxes	2,921	1,756	10,258	4,492
Net income	$ 11,568	$ 5,764	$ 45,624	$ 19,404
Net income per share:
Basic (in dollars per share)	$ 0.48	$ 0.23	$ 1.90	$ 0.77
Diluted (in dollars per share)	$ 0.47	$ 0.22	$ 1.86	$ 0.75
Weighted average shares used in per share calculation:
Basic (in shares)	24,059	25,494	24,065	25,320
Diluted (in shares)	24,466	25,932	24,551	25,933
Products [Member]
Net revenues:
Total net revenues	$ 63,798	$ 45,571	$ 211,521	$ 147,322
Costs of net revenues:
Cost of products and service	25,589	21,349	85,417	72,164
Service [Member]
Net revenues:
Total net revenues	12,792	11,104	35,986	33,094
Costs of net revenues:
Cost of products and service	$ 7,332	$ 4,614	$ 19,929	$ 15,368