Note 7 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended		58 Months Ended
	Aug. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2020	Nov. 30, 2016
Stock Repurchased During Period, Value					$ 127
Proceeds from Issuance of Preferred Stock and Preference Stock				$ 0	85,000
Dividends, Preferred Stock, Total		$ 1,340	$ 425	$ 3,962	425
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity, Shares Issued (in shares)		85,000		85,000		85,000	85,000
Deferred Offering Costs		$ 2,900		$ 2,900		$ 2,900
Dividends, Preferred Stock, Total		$ 1,300	400	$ 4,000	$ 400
Preferred Stock, Convertible, Shares Issuable (in shares)		9,500,000		9,500,000		9,500,000
Series A Redeemable Convertible Preferred Stock [Member] | Private Placement [Member]
Temporary Equity, Shares Issued (in shares)	85,000
Temporary Equity, Redemption Price Per Share (in dollars per share)	$ 1,000
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 85,000
Preferred Stock, Dividend Rate, Percentage	6.00%
Convertible Preferred Stock, Conversion Price (in dollars per share)	$ 9.50
Common Stock [Member]
Stock Repurchased During Period, Shares (in shares)					8,517
Stock Repurchased During Period, Value					$ (0)
Dividends, Preferred Stock, Total		$ (0)	$ (0)	$ (0)	$ (0)
Stock and Warrant Repurchase Plan [Member]
Stock Repurchase Program, Authorized Amount								$ 35,000
Warrants Repurchased During Period (in shares)						6,011,926
Warrants Repurchased During Period, Value						$ 14,700
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 12,000		$ 12,000		$ 12,000
Stock and Warrant Repurchase Plan [Member] | Common Stock [Member]
Stock Repurchased During Period, Shares (in shares)						875,218
Stock Repurchased During Period, Value						$ 8,300