Note 5 - Income Per Share - Weighted Average Shares Outstanding (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income	$ 37,029	$ 29,005	$ 274,161	$ 195,537
Weighted average basic shares outstanding (in shares)	35,568,775	35,555,742	35,308,668	35,246,893
Basic income per common share (in dollars per share)			$ 0.01	$ 0.01
us-gaap_EarningsPerShareDilutedAbstract
Net income allocable to common shareholders	$ 37,029	$ 29,005	$ 274,161	$ 195,537
Weighted average basic shares outstanding (in shares)	35,568,775	35,555,742	35,308,668	35,246,893
us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract
Stock options (in shares)	76,347	82,200	70,364	75,400
Weighted average dilutive shares outstanding (in shares)	35,876,540	35,862,205	35,594,805	35,524,857
Dilutive income per common share (in dollars per share)			$ 0.01	$ 0.01
Restricted Stock [Member]
us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract
Stock options (in shares)	231,418	224,263	215,773	202,564