Note 9 - Preferred Stock and Common Stock Warrants (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended			3 Months Ended	6 Months Ended	12 Months Ended
	Jan. 18, 2022	Jul. 31, 2021	Apr. 30, 2021	Mar. 31, 2021	Mar. 31, 2021	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021	Dec. 31, 2019
Gain (Loss) on Revaluation of Warrants							$ (2,533)	$ 7,870
Series A Convertible Preferred Stock [Member]
Temporary Equity, Shares Outstanding (in shares)							73,713,000	65,507,000		58,197
Temporary Equity, Par or Stated Value Per Share (in dollars per share)										$ 0.0001
Preferred Stock, Convertible, Conversion Price (in dollars per share)							$ 6.53
Series B Convertible Preferred Stock [Member]
Temporary Equity, Shares Outstanding (in shares)							70,433,000	62,612,000		55,645
Temporary Equity, Par or Stated Value Per Share (in dollars per share)										$ 0.0001
Preferred Stock, Convertible, Conversion Price (in dollars per share)							$ 6.57
Series C Convertible Preferred Stock [Member]
Temporary Equity, Shares Outstanding (in shares)							42,490,000	0
Temporary Equity, Par or Stated Value Per Share (in dollars per share)		$ 1,000	$ 1,000	$ 0.0001	$ 0.0001
Temporary Equity, Stock Issued During Period, Shares, New Issues (in shares)		5,000	10,000		24,500
Temporary Equity, Issued Price Per Share (in dollars per share)				$ 1,000	$ 1,000
Temporary Equity, Stock Issued During Period, Value, New Issues		$ 5,000	$ 10,000	$ 24,500
Temporary Equity, Stock Issued During Period, Shares Issued for Services (in shares)		100	200	490
Preferred Stock, Convertible, Conversion Price (in dollars per share)							$ 3.28
Convertible Preferred Stock [Member]
Temporary Equity, Issued Price Per Share (in dollars per share)									$ 1,000
Temporary Stock, Threshold Trading Days for Conversion (Year)							60 years
Temporary Stock, Threshold Consecutive Trading Days for Conversion (Year)							90 years
Temporary Stock, Conversion Price Minimum Percentage							175.00%
Temporary Stock, Maximum Business Days Following FID Event for Conversion (Year)							10 years
Temporary Equity, Dividend Rate Percentage						12.00%
Dividends, Preferred Stock, Paid-in-kind							$ 18,200	$ 14,300
Convertible Preferred Stock [Member] | Subsequent Event [Member]
Dividends, Preferred Stock, Paid-in-kind	$ 5,700
Common Stock Warrants [Member]
Exercise of Warrants, Percent of Fully Diluted Common Stock Acquirable							0.86%	1.42%
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)							$ 0.01
Warrants and Rights Outstanding, Term (Year)							3 years
Exercise of Warrants, Threshold Trading Days (Year)							60 years
Exercise of Warrants, Threshold Consecutive Trading Days (Year)							90 years