Note 9 - Earnings Per Share - Computation of 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 income (loss)		$ 10,203,436	$ (3,487,971)	$ 15,469,713	$ (6,581,114)
Weighted average shares used to compute basic EPS (in shares)		40,082,467	39,072,394	39,994,386	35,592,366
Dilutive effect of share-based awards (in shares)	[1]	257,282		247,531
Weighted average shares used to compute diluted EPS (in shares)		40,339,749	39,072,394	40,241,917	35,592,366
Basic (in dollars per share)		$ 0.25	$ (0.09)	$ 0.39	$ (0.18)
Diluted (in dollars per share)		$ 0.25	$ (0.09)	$ 0.38	$ (0.18)

[1] The 2017 periods exclude the shares issuable under outstanding option awards as their effect would have been antidilutive.