Note 16 - Stock Based Compensation - Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Options outstanding (in shares) | shares	3,005,825
Options outstanding, weighted-average exercise price (in dollars per share)	$ 4.98
Options exercisable (in shares) | shares	1,346,723
Options exercisable, weighted-average exercise price (in dollars per share)	$ 3.55
Range 1 [Member]
Lower range limit (in dollars per share)	1.55
Upper range limit (in dollars per share)	$ 3.53
Options outstanding (in shares) | shares	559,075
Options outstanding, weighted-average remaining contractual life (Year)	4 years 182 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 2.53
Options exercisable (in shares) | shares	546,075
Options exercisable, weighted-average exercise price (in dollars per share)	$ 2.50
Range 2 [Member]
Lower range limit (in dollars per share)	3.55
Upper range limit (in dollars per share)	$ 3.95
Options outstanding (in shares) | shares	757,150
Options outstanding, weighted-average remaining contractual life (Year)	6 years 182 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 3.62
Options exercisable (in shares) | shares	404,112
Options exercisable, weighted-average exercise price (in dollars per share)	$ 3.64
Range 3 [Member]
Lower range limit (in dollars per share)	3.99
Upper range limit (in dollars per share)	$ 7.85
Options outstanding (in shares) | shares	761,600
Options outstanding, weighted-average remaining contractual life (Year)	6 years 328 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 4.43
Options exercisable (in shares) | shares	376,536
Options exercisable, weighted-average exercise price (in dollars per share)	$ 4.73
Range 4 [Member]
Lower range limit (in dollars per share)	8
Upper range limit (in dollars per share)	$ 9.50
Options outstanding (in shares) | shares	928,000
Options outstanding, weighted-average remaining contractual life (Year)	9 years
Options outstanding, weighted-average exercise price (in dollars per share)	$ 8.03
Options exercisable (in shares) | shares	20,000
Options exercisable, weighted-average exercise price (in dollars per share)	$ 8