Note 18 - Quarterly Financial Data (Unaudited) (Details) - Summary of Quarterly Financial Data (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Quarterly Financial Data [Abstract]
Revenue	$ 75,703	$ 78,335	$ 68,436	$ 60,061	$ 63,560	$ 65,347	$ 57,714	$ 51,470	$ 282,535	$ 238,091	$ 213,813
Cost of revenue	34,744	35,872	31,337	27,964	29,266	30,053	26,786	24,085	129,917	110,190	100,665
Gross profit	40,959	42,463	37,099	32,097	34,294	35,294	30,928	27,385	152,618	127,901	113,148
Operating expenses:
Research and development	14,941	14,679	13,368	15,603	12,487	12,643	12,478	12,123
Selling, general and administrative	16,787	17,006	16,853	16,109	13,683	13,891	13,793	13,258	66,755	54,624	50,018
Litigation expense (benefit), net	66	332	274	(8,700)	84	104	(257)	(301)
Total operating expenses	31,794	32,017	30,495	23,012	26,254	26,638	26,014	25,080	117,318	103,986	95,869
Income from operations	9,165	10,446	6,604	9,085	8,040	8,656	4,914	2,305	35,300	23,915	17,279
Interest and other income, net	407	202	295	190	(57)	(59)	218	(10)
Income before income taxes	9,572	10,648	6,899	9,275	7,983	8,597	5,132	2,295	36,392	24,007	17,890
Income tax provision (benefit)	712	(573)	502	257	484	1,187	(357)	(204)	897	1,109	2,134
Net income	$ 8,860	$ 11,221	$ 6,397	$ 9,018	$ 7,499	$ 7,410	$ 5,489	$ 2,499	$ 35,495	$ 22,898	$ 15,756
Net income per share:
Basic (in Dollars per share)	$ 0.23	$ 0.29	$ 0.17	$ 0.23	$ 0.20	$ 0.20	$ 0.15	$ 0.07	$ 0.92	$ 0.61	$ 0.45
Diluted (in Dollars per share)	$ 0.22	$ 0.28	$ 0.16	$ 0.23	$ 0.19	$ 0.19	$ 0.14	$ 0.07	$ 0.89	$ 0.59	$ 0.43
Weighted-average shares outstanding:
Basic (in Shares)	38,807	38,785	38,684	38,470	38,328	37,910	37,053	36,259
Diluted (in Shares)	40,321	39,727	39,608	39,517	39,524	39,009	38,239	37,708	39,793	38,620	36,247
Cash dividends declared per common share (in Dollars per share)	$ 0.15	$ 0.15	$ 0.15						$ 0.45		$ 1.00