Note 10 - Warrants - Warrants Assumptions (Details) - Warrants for Series A Convertible Preferred Stock [Member] |
Dec. 31, 2018
USD ($)
|
Dec. 31, 2017
USD ($)
|
Jul. 01, 2010 |
|---|---|---|---|
| Measurement Input, Risk Free Interest Rate [Member] | |||
| Risk-free interest rate | 2.28 | ||
| Measurement Input, Risk Free Interest Rate [Member] | Minimum [Member] | |||
| Risk-free interest rate | 2.56 | 0.0146 | |
| Measurement Input, Risk Free Interest Rate [Member] | Maximum [Member] | |||
| Risk-free interest rate | 2.59 | 0.0266 | |
| Measurement Input, Expected Term [Member] | Minimum [Member] | |||
| Risk-free interest rate | 6.92 | 7.92 | |
| Measurement Input, Expected Term [Member] | Maximum [Member] | |||
| Risk-free interest rate | 7.08 | 8.08 | 7 |
| Measurement Input, Price Volatility [Member] | |||
| Risk-free interest rate | 71.00 | ||
| Measurement Input, Price Volatility [Member] | Minimum [Member] | |||
| Risk-free interest rate | 76.84 | 0.736 | |
| Measurement Input, Price Volatility [Member] | Maximum [Member] | |||
| Risk-free interest rate | 0.815 |