Note 19 - Quarterly Financial Data (Unaudited) (Details) - Summary of Quarterly Financial Data - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of Quarterly Financial Data [Abstract]
Revenue	$ 86,918	$ 91,194	$ 81,416	$ 73,538	$ 75,703	$ 78,335	$ 68,436	$ 60,061	$ 333,067	$ 282,535	$ 238,091
Cost of revenue	40,001	41,754	37,287	33,855	34,744	35,872	31,337	27,964	152,898	129,917	110,190
Gross profit	46,917	49,440	44,129	39,683	40,959	42,463	37,099	32,097	180,169	152,618	127,901
Operating expenses:
Research and development	16,734	17,272	15,743	16,038	14,941	14,679	13,368	15,603	65,787	58,590	49,733
Selling, general and administrative	18,107	18,722	17,964	17,518	16,787	17,006	16,853	16,109	72,312	66,755	54,624
Litigation expense	283	136	311	270	66	332	274	(8,700)	1,000	(8,027)	(371)
Total operating expenses	35,124	36,130	34,018	33,826	31,794	32,017	30,495	23,012	139,099	117,318	103,986
Income from operations	11,793	13,310	10,111	5,857	9,165	10,446	6,604	9,085	41,070	35,300	23,915
Interest and other income (expense), net	550	(6)	235	642	407	202	295	190
Income before income taxes	12,343	13,304	10,346	6,499	9,572	10,648	6,899	9,275	42,491	36,392	24,007
Income tax provision	2,233	2,103	2,447	536	712	(573)	502	257	7,319	897	1,109
Net income	$ 10,110	$ 11,201	$ 7,899	$ 5,963	$ 8,860	$ 11,221	$ 6,397	$ 9,018	$ 35,172	$ 35,495	$ 22,898
Net income per share:
Basic (in Dollars per share)	$ 0.26	$ 0.28	$ 0.20	$ 0.15	$ 0.23	$ 0.29	$ 0.17	$ 0.23	$ 0.89	$ 0.92	$ 0.61
Diluted (in Dollars per share)	$ 0.24	$ 0.28	$ 0.19	$ 0.15	$ 0.22	$ 0.28	$ 0.16	$ 0.23	$ 0.86	$ 0.89	$ 0.59
Weighted-average shares outstanding:
Basic (in Shares)	39,615	39,592	39,570	39,105	38,807	38,785	38,684	38,470
Diluted (in Shares)	41,445	40,689	40,745	40,596	40,321	39,727	39,608	39,517	40,869	39,793	38,620
Cash dividends declared per common share (in Dollars per share)	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.15	$ 0.15	$ 0.15		$ 0.80	$ 0.45