Note 8 - Income Taxes - Provision for Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current provision:
Federal	$ 3,108,894	$ 3,045,292	$ 3,368,974
State	486,565	482,186	548,225
Total current income tax expense	3,595,459	3,527,478	3,917,199
Deferred provision (benefit):
Federal	183,520	212,563	210,343
State	21,591	76,607	(26,853)
Total deferred income provision	205,111	289,170	183,490
Total income tax expense	$ 3,800,570	$ 3,816,648	$ 4,100,689