Note 16 - Stock Based Compensation - Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Options outstanding (in shares) | shares	4,979,475
Options outstanding, weighted-average exercise price (in dollars per share)	$ 6.05
Options exercisable (in shares) | shares	2,611,960
Options exercisable, weighted-average exercise price (in dollars per share)	$ 5.28
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	516,200
Options outstanding, weighted-average remaining contractual life (Year)	2 years 182 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 2.51
Options exercisable (in shares) | shares	516,200
Options exercisable, weighted-average exercise price (in dollars per share)	$ 2.51
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	650,475
Options outstanding, weighted-average remaining contractual life (Year)	4 years 182 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 3.62
Options exercisable (in shares) | shares	648,475
Options exercisable, weighted-average exercise price (in dollars per share)	$ 3.62
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	1,928,125
Options outstanding, weighted-average remaining contractual life (Year)	5 years 255 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 5.69
Options exercisable (in shares) | shares	423,874
Options exercisable, weighted-average exercise price (in dollars per share)	$ 4.17
Range 4 [Member]
Lower range limit (in dollars per share)	8
Upper range limit (in dollars per share)	$ 9.45
Options outstanding (in shares) | shares	1,884,675
Options outstanding, weighted-average remaining contractual life (Year)	8 years 73 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 8.22
Options exercisable (in shares) | shares	1,023,411
Options exercisable, weighted-average exercise price (in dollars per share)	$ 8.19