Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Net revenues:
Total net revenues	$ 88,604	$ 64,427	$ 170,917	$ 123,741
Costs of net revenues:
Amortization of intangible assets	35	52	70	104
Total costs of net revenues	37,713	30,806	72,495	61,673
Gross profit	50,891	33,621	98,422	62,068
Operating expenses:
Research and development	12,491	9,139	22,693	17,833
Selling	10,151	7,239	19,175	15,177
General and administrative	7,465	6,591	15,206	12,898
Total operating expenses	30,107	22,969	57,074	45,908
Income from operations	20,784	10,652	41,348	16,160
Other income (expense):
Interest income	1	3	4	4
Interest expense	(49)	(19)	(145)	(59)
Other income (expense), net	(166)	274	186	271
Total other income (expense), net	(214)	258	45	216
Income before income taxes	20,570	10,910	41,393	16,376
Provision for income taxes	2,895	2,622	7,337	2,736
Net income	$ 17,675	$ 8,288	$ 34,056	$ 13,640
Net income per share:
Basic (in dollars per share)	$ 0.74	$ 0.33	$ 1.42	$ 0.54
Diluted (in dollars per share)	$ 0.72	$ 0.32	$ 1.39	$ 0.53
Weighted average shares used in per share calculation:
Basic (in shares)	23,953	25,307	24,008	25,220
Diluted (in shares)	24,442	25,906	24,488	25,880
Products [Member]
Net revenues:
Total net revenues	$ 76,704	$ 53,576	$ 147,723	$ 101,751
Costs of net revenues:
Cost of products and service	31,235	25,337	59,828	50,815
Service [Member]
Net revenues:
Total net revenues	11,900	10,851	23,194	21,990
Costs of net revenues:
Cost of products and service	$ 6,443	$ 5,417	$ 12,597	$ 10,754