Note 17 - Supplementary Data - Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Product revenue	$ 16,667		$ 11,024		$ 11,973		$ 10,051		$ 15,211		$ 12,112		$ 10,484		$ 5,864		$ 49,715	$ 43,671	$ 30,426
Product cost of revenue	5,971		3,968		4,236		3,674		6,796		4,948		4,836		2,531		17,849	19,111	13,713
Product gross profit	10,696		7,056		7,737		6,377		8,415		7,164		5,648		3,333		31,866	24,560	16,713
License and development revenue	1,250		1,250		1,250		1,250		1,042								5,000	1,042	0
General and administrative	3,779	[2]	3,971	[2]	3,992	[2]	4,884	[2]	4,543	[3]	3,590	[3]	5,362	[3]	6,278	[3]	16,626	19,773	14,139
Sales and marketing	2,599		2,512		1,935		2,070		2,704		2,195		1,994		2,433		9,116	9,326	10,525
Research and development	2,730		2,319		2,422		2,665		2,242		1,474		1,410		2,533		10,136	7,659	9,690
Amortization of intangibles	158		158		158		157		159		159		158		159		631	635	842
Income (loss) from operations	2,680		(654)		480		(2,149)		(191)		(254)		(3,276)		(8,070)		357	(11,791)	(18,483)
Net income (loss)	$ 3,123		$ (579)		$ 456		$ (1,966)		$ 312		$ (340)		$ (3,327)		$ (8,283)		$ 1,034	$ (11,638)	$ (18,705)
Basic (in dollars per share)	$ 0.06		$ (0.01)		$ 0.01		$ (0.04)		$ 0.01		$ (0.01)		$ (0.06)		$ (0.16)		$ 0.02	$ (0.22)	$ (0.36)
Diluted (in dollars per share)	$ 0.06		$ (0.01)		$ 0.01		$ (0.04)		$ 0.01		$ (0.01)		$ (0.06)		$ (0.16)		$ 0.02	$ (0.22)	$ (0.36)

[1] Quarterly results may not add up to annual results due to rounding.

[2] The increase in general and administrative expense in the first quarter of 2016 was substantially related to the termination of the former General Counsel.

[3] The increases in general and administrative expense in the first and second quarters of 2015 were substantially related to the resignation of our former Chief Executive Officer and the termination of the former Senior Vice-President of Sales.