Note 12 - Common Stock - Assumptions (Details)	May 04, 2021	May 03, 2021	Jan. 19, 2021	Jan. 18, 2021	Apr. 20, 2020	Apr. 15, 2020	Apr. 14, 2020
Measurement Input, Expected Term [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input					5
Measurement Input, Price Volatility [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input					84.1
Measurement Input, Risk Free Interest Rate [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input					0.35
Measurement Input, Expected Dividend Rate [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input					0
Warrant [Member] | Measurement Input, Exercise Price [Member]
Warrants and Rights Outstanding, Measurement Input						6.10	15.50
Warrant [Member] | Measurement Input, Exercise Price [Member] | Series B Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			3.40	6.10
Warrant [Member] | Measurement Input, Exercise Price [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			3.40	6.37
Warrant [Member] | Measurement Input, Exercise Price [Member] | Series B, A-2 and B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input	2.82	3.40
Warrant [Member] | Measurement Input, Share Price [Member]
Warrants and Rights Outstanding, Measurement Input						6.30	6.30
Warrant [Member] | Measurement Input, Share Price [Member] | Series B Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			3.19	3.19
Warrant [Member] | Measurement Input, Share Price [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			3.19	3.19
Warrant [Member] | Measurement Input, Share Price [Member] | Series B, A-2 and B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input	3.01	3.01
Warrant [Member] | Measurement Input, Expected Term [Member]
Warrants and Rights Outstanding, Measurement Input						2.8	2.8
Warrant [Member] | Measurement Input, Expected Term [Member] | Series B Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			3.9	3.9
Warrant [Member] | Measurement Input, Expected Term [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			4.3	4.3
Warrant [Member] | Measurement Input, Expected Term [Member] | Series B, A-2 and B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input	3.6	3.6
Warrant [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input						0.97	0.97
Warrant [Member] | Measurement Input, Price Volatility [Member] | Series B Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			0.90	0.90
Warrant [Member] | Measurement Input, Price Volatility [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			0.90	0.90
Warrant [Member] | Measurement Input, Price Volatility [Member] | Series B, A-2 and B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input	0.80	0.80
Warrant [Member] | Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input						0.0027	0.0027
Warrant [Member] | Measurement Input, Risk Free Interest Rate [Member] | Series B Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			0.0033	0.0033
Warrant [Member] | Measurement Input, Risk Free Interest Rate [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			0.0033	0.0033
Warrant [Member] | Measurement Input, Risk Free Interest Rate [Member] | Series B, A-2 and B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input	0.0058	0.0058
Warrant [Member] | Measurement Input, Expected Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input						0	0
Warrant [Member] | Measurement Input, Expected Dividend Rate [Member] | Series B Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			0	0
Warrant [Member] | Measurement Input, Expected Dividend Rate [Member] | Series A-2 and Series B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input			0	0
Warrant [Member] | Measurement Input, Expected Dividend Rate [Member] | Series B, A-2 and B-2 Warrants [Member]
Warrants and Rights Outstanding, Measurement Input	0	0