Note 3 - Basis of Presentation and Summary of Significant Accounting Policies - Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net (loss) income	$ (2,765,181)	$ 20,387,741	$ (6,079,142)	$ (8,251,037)
Accretion of Series A cumulative preferred dividends		(487,460)	(85,993)	(546,305)
Undistributed earnings allocated to participating securities		(10,416,153)
Deemed dividend related to the make-whole provision for the conversion of Series A preferred stock into common			(8,167,895)
Net (loss) income attributable to common stockholders	$ (2,765,181)	$ 19,900,281	$ (14,333,030)	$ (8,797,342)
Weighted average shares outstanding, basic (in shares)	50,546,021	10,828,063	46,357,478	10,582,521
Net (loss) income per share of common stock, basic (in dollars per share)	$ (0.05)	$ 0.88	$ (0.31)	$ (0.83)
Add change in fair value of warrant liability		$ (23,387,850)		$ (10,468,176)
Diluted net loss	$ (2,765,181)	$ (13,903,722)	$ (14,333,030)	$ (19,265,518)
Add shares from dilutive warrants (in shares)		3,044,569		1,756,865
Common stock equivalents (in shares)	50,546,021	13,872,632	46,357,478	12,339,386
Net (loss) income per share of common stock, diluted (in dollars per share)	$ (0.05)	$ (1)	$ (0.31)	$ (1.56)