Note 3 - Basis of Presentation and Summary of Significant Accounting Policies - Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic net income (loss) per common share calculation:
Net income (loss)	$ 5,096,856	$ (5,436,553)	$ (3,154,181)	$ (15,465,912)
Accretion of Series A cumulative preferred dividends	(366,641)		(912,946)
Undistributed earnings to participating securities	(1,838,354)
Net income (loss) attributable to common stockholders	$ 2,891,861	$ (5,436,553)	$ (4,067,127)	$ (15,465,912)
Weighted average shares outstanding, basic (in shares)	13,937,869	10,333,898	11,709,128	10,198,491
Net income (loss) per share of common stock, basic (in dollars per share)	$ 0.21	$ (0.53)	$ (0.35)	$ (1.52)
Diluted net income (loss) per common share calculation:
Net income (loss) attributable to common stockholders	$ 2,891,861	$ (5,436,553)	$ (4,067,127)	$ (15,465,912)
Change in fair value of warrant liability			(18,909,792)
Interest on convertible debt	28,891
Diluted net loss	$ 2,920,752	$ (5,436,553)	$ (22,976,919)	$ (15,465,912)
Weighted average shares outstanding, basic (in shares)	13,937,869	10,333,898	11,709,128	10,198,491
Common stock equivalents arising from stock options (in shares)	20,608
Common stock equivalents arising from warrants (in shares)			816,579
Common stock equivalents arising from convertible debt (in shares)	756,376
Common stock equivalents (in shares)	14,714,853	10,333,898	12,525,707	10,198,491
Net income (loss) per share of common stock, diluted (in dollars per share)	$ 0.20	$ (0.53)	$ (1.83)	$ (1.52)