Note 2 - Significant Accounting Policies - Earnings Per Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income	$ 2,059,997	$ 1,000,350	$ 1,820,915	$ 1,520,997	$ 2,338,758	$ 1,111,344	$ 1,507,896	$ 1,444,407	$ 6,402,259	$ 6,402,405	$ 7,706,921
Weighted average common shares outstanding (in shares)	9,188,483	9,188,483	9,209,446	9,698,951	9,692,860	10,175,650	10,212,933	10,211,333	9,301,867	10,077,506	10,203,063
Earnings per share – basic (in dollars per share)	$ 0.23	$ 0.11	$ 0.19	$ 0.16	$ 0.24	$ 0.11	$ 0.15	$ 0.14	$ 0.69	$ 0.64	$ 0.76
DILUTED
Net income	$ 2,059,997	$ 1,000,350	$ 1,820,915	$ 1,520,997	$ 2,338,758	$ 1,111,344	$ 1,507,896	$ 1,444,407	$ 6,402,259	$ 6,402,405	$ 7,706,921
Weighted average common shares outstanding (in shares)	9,188,483	9,188,483	9,209,446	9,698,951	9,692,860	10,175,650	10,212,933	10,211,333	9,301,867	10,077,506	10,203,063
Effect of restricted stock awards and assumed exercise of stock options (in shares)									19,691	25,254	38,058
Weighted average common shares outstanding, assuming dilution (in shares)	9,301,867	9,206,382	9,227,941	9,718,453	9,712,571	10,199,092	10,241,164	10,241,096	9,321,558	10,102,760	10,241,121
Earnings per share - diluted (in dollars per share)	$ 0.23	$ 0.11	$ 0.19	$ 0.16	$ 0.24	$ 0.11	$ 0.15	$ 0.14	$ 0.69	$ 0.63	$ 0.75
Outstanding options and restricted stock awards excluded as anti-dilutive (in shares)									31,477	60,433