Note 13 - Income Taxes (Details) - Summary of Deferred Tax Assets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Deferred Tax Assets [Abstract]
Net operating loss carryforwards	$ 29,217	$ 26,304	$ 26,560
Federal and state tax credits	12,126	9,941	2,777
Deferred revenue		1,147us-gaap_DeferredTaxAssetsDeferredIncome	1,139us-gaap_DeferredTaxAssetsDeferredIncome
Accrued expenses	478	332	155
Patents	531	612	692
Other	100us-gaap_DeferredTaxAssetsOther	300us-gaap_DeferredTaxAssetsOther	27us-gaap_DeferredTaxAssetsOther
	42,452us-gaap_DeferredTaxAssetsGross	38,636us-gaap_DeferredTaxAssetsGross	31,350us-gaap_DeferredTaxAssetsGross
Valuation allowance	$ (42,452)	$ (38,636)	$ (31,350)

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred income.

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