Note 4 - Earnings Per Share - Basic and Diluted (Details) - USD ($)		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Net income		$ 9,184,965	$ 6,373,489
Basic earnings (loss) per common share (in dollars per share) (in dollars per share)		$ 0.70	$ 0.54
Diluted earnings (loss) per common share (in dollars per share) (in dollars per share)		$ 0.68	$ 0.53
Weighted average common shares outstanding (in shares)	[1]	13,133,382	11,793,620
Weighted average common shares issuable upon exercise of stock options and under the employee stock purchase plan (in shares)	[2]	355,035	160,329
Weighted average common and common equivalent shares outstanding (in shares)		13,488,417	11,953,949

[1] The increase in weighted average common shares outstanding from 2014 to 2015 was primarily due to the common stock issuance discussed in Note 16 to the Consolidated Financial Statements. The increase in weighted average common shares outstanding from 2015 to 2016 was primarily due to the common stock issuance discussed in Note 2 to the Consolidated Financial Statements.

[2] Excludes anti-dilutive shares of 17,739, 36,572, and 124,983 at December 31, 2016, 2015 and 2014, respectively.