Note 1 - Nature of Operations and Summary of Significant Accounting Policies - Earnings Per Common Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income available to common shareholders	$ 2,384,876	$ 3,934,242	$ (342,984)	$ 1,355,745	$ 418,467	$ 1,717,383	$ 1,592,573	$ 1,429,241	$ 7,331,879	$ 5,157,664	$ 5,594,011
Weighted average common shares outstanding (in shares)									4,410,422	4,372,262	4,363,949
Effect of dilutive securities (in shares)									72,261	68,685	56,299
Weighted average diluted shares outstanding (in shares)									4,482,683	4,440,947	4,420,248
Basic income per common share (in dollars per share)	$ 0.54	$ 0.89	$ (0.08)	$ 0.31	$ 0.10	$ 0.39	$ 0.36	$ 0.33	$ 1.66	$ 1.18	$ 1.28
Diluted income per common share (in dollars per share)	$ 0.53	$ 0.88	$ (0.08)	$ 0.30	$ 0.09	$ 0.39	$ 0.36	$ 0.32	$ 1.64	$ 1.16	$ 1.27