Note 19 - Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 166,738	$ 168,813	$ 151,007	$ 141,363	$ 153,497	$ 159,975	$ 139,761	$ 129,150	$ 627,921	$ 582,382	$ 470,929
Cost of revenue	74,802	75,655	67,782	63,357	68,904	70,957	62,197	57,655	281,596	259,714	212,646
Gross profit	91,936	93,158	83,225	78,006	84,593	89,018	77,564	71,495	346,325	322,668	258,283
Research and development	27,011	27,742	27,545	25,458	22,735	25,630	23,481	21,609	107,757	93,455	82,359
Selling, general and administrative	33,240	34,692	35,058	30,553	28,372	29,552	28,561	27,318	133,542	113,803	97,257
Litigation expense	991	692	503	278	409	343	640	531
Total operating expenses	61,242	63,126	63,106	56,289	51,516	55,525	52,682	49,458	243,763	209,180	180,859
Income from operations	30,694	30,032	20,119	21,717	33,077	33,493	24,882	22,037	102,562	113,488	77,424
Interest and other income (expense), net	2,731	2,257	2,229	3,341	(393)	2,714	2,232	440	10,558	4,994	5,520
Income before income taxes	33,425	32,289	22,348	25,058	32,684	36,207	27,114	22,477	113,120	118,482	82,944
Income tax expense (benefit)	989	2,761	1,655	(1,123)	5,046	4,639	2,908	621	4,281	13,214	17,741
Net income	$ 32,436	$ 29,528	$ 20,693	$ 26,181	$ 27,638	$ 31,568	$ 24,206	$ 21,856	$ 108,839	$ 105,268	$ 65,203
Earnings per share, basic (in dollars per share)	$ 0.75	$ 0.68	$ 0.48	$ 0.61	$ 0.65	$ 0.75	$ 0.57	$ 0.52	$ 2.52	$ 2.49	$ 1.58
Earnings per share, diluted (in dollars per share)	$ 0.70	$ 0.64	$ 0.45	$ 0.58	$ 0.61	$ 0.71	$ 0.55	$ 0.49	$ 2.38	$ 2.36	$ 1.50
Weighted-average shares outstanding, basic (in shares)	43,496	43,308	43,109	42,749	42,467	42,362	42,237	41,922
Diluted (in shares)	46,503	45,833	45,483	45,232	45,058	44,669	44,400	44,282	45,763	44,602	43,578