Note 5 - Earnings Per Share - Basic and Diluted (Details) - USD ($)		3 Months Ended				6 Months Ended
		Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015
Net income (loss)		$ 6,676,467	$ 6,373,489	$ (523,818)	$ 4,177,889	$ 13,049,956	$ 3,654,071
Basic EPS (in dollars per share)		$ 0.54		$ (0.05)		$ 1.08	$ 0.41
Diluted EPS (in dollars per share)		$ 0.53		$ (0.05)		$ 1.07	$ 0.40
Weighted average common shares outstanding (in shares)	[1]	12,335,077		9,946,744		12,064,349	8,961,327
Weighted average common shares issuable upon exercise of stock options and under the employee stock purchase plan** (in shares)	[2]	181,397				170,863	137,370
Weighted average common and common equivalent shares outstanding** (in shares)		12,516,474		9,946,744		12,235,212	9,098,697

[1] The increase in the weighted average common shares outstanding was primarily due to the common stock issuance discussed in Note 9 to the Consolidated Financial Statements.

[2] In accordance with U.S. GAAP, the common equivalent shares are not considered in the calculation of diluted EPS in periods when the numerator is a net loss.