Note 12 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Research tax credits	$ 9,817	$ 8,869
Deferred compensation	6,752	5,038
Stock-based compensation	7,283	1,912
Other expenses not currently deductible	3,974	3,519
Depreciation and amortization	161	(52)
Total deferred tax assets	27,987	19,286
Valuation allowance	(27,354)	(18,614)
Net deferred tax assets	$ 633	$ 672