Note 18 - Shareholders' Equity - Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Options outstanding (in shares)	188,900	234,100
Options outstanding, weighted average exercise price (in dollars per share)	$ 5.08	$ 5.77
Options outstanding, aggregate intrinsic value	$ 704,350	$ 834,625	$ 319,483
Options outstanding, weighted average remaining contractual term (Year)	4 years 277 days	5 years 240 days	5 years 317 days
Exercised (in shares)	(51,900)	(1,900)
Exercised, weighted average exercise price (in dollars per share)	$ 4.73	$ 5.29
Exercised, aggregate intrinsic value	$ 245,450	$ 4,789
Exercised, weighted average remaining contractual term (Year) (Year)	4 years 153 days	3 years 120 days
Forfeited (in shares)	(2,500)	(43,300)
Forfeited, weighted average exercise price (in dollars per share)	$ 4.05	$ 8.81
Options outstanding (in shares)	134,500	188,900	234,100
Options outstanding, weighted average exercise price (in dollars per share)	$ 5.24	$ 5.08	$ 5.77
Exercisable at December 31, 2017 (in shares)	118,920
Exercisable at December 31, 2017 (in dollars per share)	$ 5.13
Exercisable at December 31, 2017	$ 609,596
Exercisable at December 31, 2017 (Year)	4 years 186 days