Note 6 - Fair Value of Measurements - Assets and Liabilities at Fair Value on a Recurring Basis (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Earn-out milestone liability	$ 12,518,054	$ 13,188,226
Fair Value, Measurements, Recurring [Member]
Short-term investments, fair value		1,680,000
Earn-out milestone liability	12,518,054	13,188,226
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Short-term investments, fair value		1,680,000
Earn-out milestone liability
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Short-term investments, fair value
Earn-out milestone liability	$ 12,518,054	$ 13,188,226