Note 1 - Organization and Summary of Significant Accounting Policies - Adjustments for Adoption of New Lease Standard (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating lease right-of-use assets		$ 3,928
Accrued liabilities		5,528		4,540
Operating lease liabilities		970
Operating lease liabilities, net of current portion		3,640
Accumulated deficit		$ (398,106)		$ (345,019)
Accounting Standards Update 2016-02 [Member]
Operating lease right-of-use assets			$ 4,730
Accrued liabilities	[1]		(100)
Operating lease liabilities			484
Operating lease liabilities, net of current portion			4,610
Deferred rent, net of current portion			(416)
Accumulated deficit	[2]		$ (153)

[1] Represents current portion of Deferred rent reclassified to Operating lease liabilities.

[2] Represents cumulative-effect adjustment upon adoption of ASU No. 2016-02.