Note 11 - Stock-based Compensation - Non-vested Restricted Stock (Details) - Restricted Stock [Member]	6 Months Ended
	Jun. 30, 2020 $ / shares shares
Non-vested (in shares) | shares	1,308,613
Non-vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 1.91
Granted (in shares) | shares	349,750
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0.98
Vested (in shares) | shares	(900,180)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 1.60
Canceled or forfeited (in shares) | shares	(6,974)
Canceled or forfeited, weighted average grant date fair value (in dollars per share) | $ / shares	$ 1.90
Non-vested (in shares) | shares	751,209
Non-vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 1.81