Note 1 - Organization and Operations (Details Textual) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Aug. 02, 2017 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) $ / shares shares	Mar. 31, 2019 shares	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares
Entity Number of Employees		4			4
Preferred Stock, Par or Stated Value Per Share | $ / shares		$ 0.001			$ 0.001	$ 0.001
Cash, Cash Equivalents, and Short-term Investments, Total		$ 10,800			$ 10,800
Retained Earnings (Accumulated Deficit), Ending Balance		$ (222,316)			$ (222,316)	$ (210,470)
Common Stock [Member]
Stock Issued During Period, Shares, Conversion of Convertible Securities | shares			341,743		341,743
Series A Convertible Preferred Stock [Member]
Stock Issued During Period, Shares, New Issues | shares	22,000
Preferred Stock, Par or Stated Value Per Share | $ / shares	$ 0.001	$ 0.001			$ 0.001
Shares Issued, Price Per Share | $ / shares	$ 1,000
Proceeds from Issuance of Convertible Preferred Stock	$ 22,000
Conversion of Stock, Shares Converted | shares					340
Forecast [Member]
Severance Costs				$ 2,900