Note 7 - Share-based Compensation - Restricted Stock Activity (Details) - Restricted Stock [Member]	3 Months Ended
	Mar. 31, 2020 $ / shares shares
Unvested outstanding at beginning of period (in shares) | shares	429,399
Unvested outstanding at beginning of period (in dollars per share) | $ / shares	$ 13.25
Unvested granted (in shares) | shares	175,971
Granted, grant date fair value (in dollars per share) | $ / shares	$ 9.43
Vested (in shares) | shares	(53,026)
Vested, grant date fair value (in dollars per share) | $ / shares	$ 12.90
Forfeited (in shares) | shares	(7,000)
Forfeited, grant date fair value (in dollars per share) | $ / shares	$ 15.92
Unvested outstanding (in shares) | shares	545,344
Unvested outstanding, grant date fair value (in dollars per share) | $ / shares	$ 12.01