Note 4 - Fair Values of Financial Instruments - Assets and Liabilities at Fair Value On a Recurring Basis (Details) - USD ($) |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Fair value | $ 12,724,020 | |
| Earn-out milestone liability (Note 12) | 12,538,525 | $ 13,188,226 |
| Fair Value, Measurements, Recurring [Member] | ||
| Fair value | 12,724,020 | 1,680,000 |
| Earn-out milestone liability (Note 12) | 12,538,525 | 13,188,226 |
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | ||
| Fair value | 12,724,020 | 1,680,000 |
| Earn-out milestone liability (Note 12) | ||
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | ||
| Fair value | ||
| Earn-out milestone liability (Note 12) | $ 12,538,525 | $ 13,188,226 |