Note 9 - Preferred Stock and Common Stock Warrants (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended			9 Months Ended	12 Months Ended
	Jan. 15, 2020	May 31, 2019	Sep. 30, 2018	Aug. 31, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Revaluation of Warrants						$ (2,657)	$ 164
Proceeds from Issuance of Convertible Preferred Stock and Common Stock Warrant, Net							76,951
Series A Warrants [Member]
Exercise of Warrants, Percent of Fully Diluted Common Stock Acquirable						0.71%
Class of Warrant or Right, Exercise Price of Warrants or Rights						$ 0.01
Allocation of Net Cash Proceeds
Proceeds from Issuance of Convertible Preferred Stock and Common Stock Warrant, Net							4,859
Series B Warrants [Member]
Exercise of Warrants, Percent of Fully Diluted Common Stock Acquirable						0.71%
Class of Warrant or Right, Exercise Price of Warrants or Rights						$ 0.01
Allocation of Net Cash Proceeds
Proceeds from Issuance of Convertible Preferred Stock and Common Stock Warrant, Net						$ 1,936	2,746
Common Stock Warrants [Member]
Exercise of Warrants, Threshold Trading Days						60 days
Exercise of Warrants, Threshold Consecutive Trading Days						90 days
Common Stock [Member]
Stock Issued During Period, Shares, New Issues						10,094,000
Common Stock [Member] | Backstop Agreements [Member]
Stock Issued During Period, Shares, New Issues				413,658
Series A Convertible Preferred Stock [Member]
Temporary Equity, Stock Issued During Period, Shares, New Issues				50,000
Temporary Equity, Par or Stated Value Per Share				$ 0.0001
Temporary Equity, Issued Price Per Share				$ 1,000
Temporary Equity, Stock Issued During Period, Value, New Issues				$ 50,000
Temporary Equity, Stock Issued During Period, Shares Issued for Services				1,000
Allocation of Net Cash Proceeds							(2,530)
Proceeds from Issuance of Convertible Preferred Stock and Common Stock Warrant, Net							41,079
Preferred Stock, Convertible, Conversion Price						$ 7.50
Accretion of Discount Amount						$ 2,500
Series A Convertible Preferred Stock [Member] | Fund Purchasers [Member]
Preferred Stock, Convertible, Conversion Price						$ 5.58
Series A Convertible Preferred Stock [Member] | HGC [Member]
Preferred Stock, Convertible, Conversion Price						$ 6.24
Series A Convertible Preferred Stock [Member] | Additional Paid-in Capital [Member]
Allocation of Net Cash Proceeds							2,500
Series B Convertible Preferred Stock [Member]
Temporary Equity, Stock Issued During Period, Shares, New Issues		20,945	29,055
Temporary Equity, Par or Stated Value Per Share			$ 0.0001
Temporary Equity, Issued Price Per Share		$ 1,000	$ 1,000
Temporary Equity, Stock Issued During Period, Value, New Issues		$ 20,945	$ 29,055
Temporary Equity, Stock Issued During Period, Shares Issued for Services		418	581
Allocation of Net Cash Proceeds
Proceeds from Issuance of Convertible Preferred Stock and Common Stock Warrant, Net						$ 19,009	$ 26,159
Convertible Preferred Stock [Member]
Temporary Equity, Issued Price Per Share					$ 1,000
Temporary Equity, Redemption Price Per Share						$ 7.34
Temporary Stock, Threshold Trading Days for Conversion						60 days
Temporary Stock, Threshold Consecutive Trading Days for Conversion						90 days
Temporary Stock, Conversion Price Minimum Percentage						175.00%
Temporary Stock, Maximum Business Days Following FID Event for Conversion						10 days
Temporary Equity, Dividend Rate Percentage					12.00%
Dividends, Preferred Stock, Paid-in-kind						$ 11,200
Proceeds from Issuance of Convertible Preferred Stock and Common Stock Warrant, Net						$ 20,945
Convertible Preferred Stock [Member] | Subsequent Event [Member]
Dividends, Preferred Stock, Paid-in-kind	$ 3,400