Note 3 - Fair Value Measurements - Assumptions on Accrued Warrant Liability (Details)	Dec. 31, 2019	Dec. 31, 2018
Measurement Input, Share Price [Member]
Warrants and Rights Outstanding, Measurement Input	0.006	0.0101
Measurement Input, Exercise Price [Member] | Minimum [Member]
Warrants and Rights Outstanding, Measurement Input	0.0364	0.0364
Measurement Input, Exercise Price [Member] | Maximum [Member]
Warrants and Rights Outstanding, Measurement Input	0.204	0.244
Measurement Input, Expected Term [Member] | Minimum [Member]
Warrants and Rights Outstanding, Measurement Input	0.0104	0.0004
Measurement Input, Expected Term [Member] | Maximum [Member]
Warrants and Rights Outstanding, Measurement Input	0.016	0.026
Measurement Input, Price Volatility [Member] | Minimum [Member]
Warrants and Rights Outstanding, Measurement Input	0.8459	0.8807
Measurement Input, Price Volatility [Member] | Maximum [Member]
Warrants and Rights Outstanding, Measurement Input	0.9824	1.0818
Measurement Input, Expected Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input	0	0
Measurement Input, Discount Rate [Member] | Minimum [Member]
Warrants and Rights Outstanding, Measurement Input	0.0158	0.0012
Measurement Input, Discount Rate [Member] | Maximum [Member]
Warrants and Rights Outstanding, Measurement Input	0.0159	0.0248