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, 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 available to common shareholders	$ 1,519,347	$ 1,541,907	$ 1,256,152	$ 1,276,605	$ 1,430,639	$ 1,418,635	$ 1,537,949	$ 1,329,544	$ 5,594,011	$ 5,716,767	$ 5,425,486
Weighted average common shares outstanding (in shares)									4,363,949	4,333,418	4,006,461
Effect of dilutive securities (in shares)									56,299	55,931	68,040
Weighted average diluted shares outstanding (in shares)									4,420,248	4,389,349	4,074,501
Basic income per common share (in dollars per share)	$ 0.35	$ 0.35	$ 0.29	$ 0.29	$ 0.33	$ 0.33	$ 0.35	$ 0.31	$ 1.28	$ 1.32	$ 1.35
Diluted income per common share (in dollars per share)	$ 0.34	$ 0.35	$ 0.28	$ 0.29	$ 0.33	$ 0.32	$ 0.35	$ 0.30	$ 1.27	$ 1.30	$ 1.33