Note 11 - Warrant Liability - The Key Assumptions Used to Value the Warrants (Details)	Mar. 31, 2020	Dec. 31, 2019	Aug. 13, 2019
Measurement Input, Price Volatility [Member] | The 2011 Warrants [Member]
Warrants assumptions		1.15
Measurement Input, Price Volatility [Member] | October 2015 Warrants [Member]
Warrants assumptions	1.91	1.84
Measurement Input, Price Volatility [Member] | The 2019 Foreign Warrants [Member]
Warrants assumptions	1.7535	1.541	1.4929
Measurement Input, Price Volatility [Member] | The 2019 Ladenburg Warrants [Member]
Warrants assumptions	1.7977	1.5994	1.5519
Measurement Input, Price Volatility [Member] | The 2019 Domestic Warrants [Member]
Warrants assumptions	1.7535	1.541	1.4929
Measurement Input, Expected Term [Member] | The 2011 Warrants [Member]
Warrants assumptions		0.18
Measurement Input, Expected Term [Member] | October 2015 Warrants [Member]
Warrants assumptions	0.58	0.83
Measurement Input, Expected Term [Member] | The 2019 Foreign Warrants [Member]
Warrants assumptions	4.88	5.13	5.5
Measurement Input, Expected Term [Member] | The 2019 Ladenburg Warrants [Member]
Warrants assumptions	4.36	4.61	5
Measurement Input, Expected Term [Member] | The 2019 Domestic Warrants [Member]
Warrants assumptions	4.88	5.13	5.5
Measurement Input, Risk Free Interest Rate [Member] | The 2011 Warrants [Member]
Warrants assumptions		0.0152
Measurement Input, Risk Free Interest Rate [Member] | October 2015 Warrants [Member]
Warrants assumptions	0.0015	0.0159
Measurement Input, Risk Free Interest Rate [Member] | The 2019 Foreign Warrants [Member]
Warrants assumptions	0.0037	0.017	0.0158
Measurement Input, Risk Free Interest Rate [Member] | The 2019 Ladenburg Warrants [Member]
Warrants assumptions	0.0034	0.0169	0.0157
Measurement Input, Risk Free Interest Rate [Member] | The 2019 Domestic Warrants [Member]
Warrants assumptions	0.0037	0.017	0.0158
Measurement Input, Expected Dividend Rate [Member] | The 2011 Warrants [Member]
Warrants assumptions		0
Measurement Input, Expected Dividend Rate [Member] | October 2015 Warrants [Member]
Warrants assumptions	0	0
Measurement Input, Expected Dividend Rate [Member] | The 2019 Foreign Warrants [Member]
Warrants assumptions	0	0	0
Measurement Input, Expected Dividend Rate [Member] | The 2019 Ladenburg Warrants [Member]
Warrants assumptions	0	0	0
Measurement Input, Expected Dividend Rate [Member] | The 2019 Domestic Warrants [Member]
Warrants assumptions	0	0	0
Measurement Input, Share Price [Member] | The 2011 Warrants [Member]
Warrants assumptions		0.0044
Measurement Input, Share Price [Member] | October 2015 Warrants [Member]
Warrants assumptions	0.0046	0.0049
Measurement Input, Share Price [Member] | The 2019 Foreign Warrants [Member]
Warrants assumptions	0.0056	0.0057	0.0075
Measurement Input, Share Price [Member] | The 2019 Ladenburg Warrants [Member]
Warrants assumptions	0.0055	0.0057	0.0074
Measurement Input, Share Price [Member] | The 2019 Domestic Warrants [Member]
Warrants assumptions	0.0056	0.0057	0.0075