Note 7 - Stockholders' Equity (Details Textual) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended		41 Months Ended
	Aug. 31, 2020	Aug. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Nov. 30, 2016
Proceeds from Issuance of Preferred Stock and Preference Stock					$ 85,000,000	$ 0
Stock Repurchased During Period, Value			$ (0)		$ 127,000	$ 23,000
Common Stock [Member]
Stock Repurchased During Period, Shares (in shares)			(0)		8,517	1,895
Stock Repurchased During Period, Value			$ (0)		$ (0)	$ (0)
Stock and Warrant Repurchase Plan [Member]
Stock Repurchase Program, Authorized Amount									$ 35,000,000.0
Warrants Repurchased During Period (in shares)							6,011,926
Warrants Repurchased During Period, Value							$ 14,700,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 12,000,000.0		$ 12,000,000.0
Stock and Warrant Repurchase Plan [Member] | Common Stock [Member]
Stock Repurchased During Period, Shares (in shares)				8,517			875,218
Stock Repurchased During Period, Value				$ 127,000			$ 8,300,000
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity, Shares Issued (in shares)			85,000		85,000			0
Dividends Payable			$ 400,000		$ 400,000
Deferred Offering Costs			$ 2,800,000		$ 2,800,000
Convertible Preferred Stock, Shares Reserved for Future Issuance (in shares)			8,900,000		8,900,000
Series A Redeemable Convertible Preferred Stock [Member] | Private Placement [Member]
Temporary Equity, Shares Issued (in shares)	85,000	85,000
Temporary Equity, Par or Stated Value Per Share (in dollars per share)	$ 0.0001	$ 0.0001
Temporary Equity, Redemption Price Per Share (in dollars per share)	$ 1,000	$ 1,000
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 85,000,000.0	$ 85,000,000.0
Preferred Stock, Dividend Rate, Percentage	6.00%	6.00%
Convertible Preferred Stock, Conversion Price (in dollars per share)	$ 9.50	$ 9.50