Note 9 - Earnings Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income (loss)		$ 6,211,328	$ (6,235,543)	$ 21,681,041	$ (12,816,658)
Weighted average shares used to compute basic EPS (in shares)		40,082,467	39,509,311	40,024,069	36,912,362
Dilutive effect of share-based awards (in shares)	[1]	246,842		247,090
Weighted average shares used to compute diluted EPS (in shares)		40,329,309	39,509,311	40,271,159	36,912,362
Basic (in dollars per share)		$ 0.15	$ (0.16)	$ 0.54	$ (0.35)
Diluted (in dollars per share)		$ 0.15	$ (0.16)	$ 0.54	$ (0.35)

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