Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue	$ 103,618	$ 106,456	$ 94,079	$ 84,512	$ 86,918	$ 91,194	$ 81,416	$ 73,538	$ 388,665	$ 333,067	$ 282,535
Cost of revenue	47,107	48,531	43,153	39,002	40,001	41,754	37,287	33,855	177,792	152,898	129,917
Gross profit	56,511	57,925	50,926	45,510	46,917	49,440	44,129	39,683	210,873	180,169	152,618
Operating expenses:
Research and development	17,974	20,472	17,876	17,321	16,734	17,272	15,743	16,038	73,643	65,787	58,590
Selling, general and administrative	21,316	22,397	21,531	17,768	18,107	18,722	17,964	17,518	83,012	72,312	66,755
Litigation expense (benefit), net	(321)	55	(8)	45	283	136	311	270	(229)	1,000	(8,027)
Total operating expenses	38,969	42,924	39,399	35,134	35,124	36,130	34,018	33,826	156,426	139,099	117,318
Income from operations	17,542	15,001	11,527	10,376	11,793	13,310	10,111	5,857	54,447	41,070	35,300
Interest and other income, net	897	780	597	543	550	(6)	235	642	2,817	1,421	1,092
Income before income taxes	18,439	15,781	12,124	10,919	12,343	13,304	10,346	6,499	57,264	42,491	36,392
Income tax provision	1,866	1,408	926	344	2,233	2,103	2,447	536	4,544	7,319	897
Net income	$ 16,573	$ 14,373	$ 11,198	$ 10,575	$ 10,110	$ 11,201	$ 7,899	$ 5,963	$ 52,720	$ 35,172	$ 35,495
Net income per share:
Basic (in dollars per share)	$ 0.41	$ 0.35	$ 0.28	$ 0.26	$ 0.26	$ 0.28	$ 0.20	$ 0.15	$ 1.30	$ 0.89	$ 0.92
Diluted (in dollars per share)	$ 0.39	$ 0.34	$ 0.27	$ 0.25	$ 0.24	$ 0.28	$ 0.19	$ 0.15	$ 1.26	$ 0.86	$ 0.89
Weighted-average shares outstanding:
Basic (in shares)									40,436	39,470	38,686
Diluted (in shares)	42,404	41,895	41,716	41,646	41,445	40,689	40,745	40,596	41,915	40,869	39,793
Cash dividends declared per common share (in dollars per share)	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.80	$ 0.80	$ 0.45