Note 11 - Stockholders' Equity and Stock Incentive Plans - Stock Options Outstanding Exercisable (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Options outstanding, number outstanding (in shares) | shares	887,728
Options outstanding, weighted average remaining contractual life (Year)	4 years 2 months 12 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 12.48
Options exercisable, number exercisable (in shares) | shares	887,728
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 12.48
Range One [Member]
Options outstanding, number outstanding (in shares) | shares	25,510
Options outstanding, weighted average remaining contractual life (Year)	2 years 10 months 24 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 5.22
Options exercisable, number exercisable (in shares) | shares	25,510
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 5.22
Range Two [Member]
Options outstanding, number outstanding (in shares) | shares	84,353
Options outstanding, weighted average remaining contractual life (Year)	1 year 10 months 24 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 6.70
Options exercisable, number exercisable (in shares) | shares	84,353
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 6.70
Range Three [Member]
Options outstanding, number outstanding (in shares) | shares	146,065
Options outstanding, weighted average remaining contractual life (Year)	9 months 18 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 8.34
Options exercisable, number exercisable (in shares) | shares	146,065
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 8.34
Range Four [Member]
Options outstanding, number outstanding (in shares) | shares	202,068
Options outstanding, weighted average remaining contractual life (Year)	3 years 10 months 24 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 9.86
Options exercisable, number exercisable (in shares) | shares	202,068
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 9.86
Range Five [Member]
Options outstanding, number outstanding (in shares) | shares	123,849
Options outstanding, weighted average remaining contractual life (Year)	4 years 10 months 24 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 11.57
Options exercisable, number exercisable (in shares) | shares	123,849
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 11.57
Range Six [Member]
Options outstanding, number outstanding (in shares) | shares	169,857
Options outstanding, weighted average remaining contractual life (Year)	6 years 10 months 24 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 17.75
Options exercisable, number exercisable (in shares) | shares	169,857
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 17.75
Range 7 [Member]
Options outstanding, number outstanding (in shares) | shares	136,026
Options outstanding, weighted average remaining contractual life (Year)	5 years 9 months 18 days
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 19.98
Options exercisable, number exercisable (in shares) | shares	136,026
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 19.98