Note 11 - Stock Options and Restricted Stock - Summary of the Status of Non-vested Shares (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Balance, non-vested (in shares)	593,833	2,531,599
Balance, non-vested, weighted average grant date fair value (in dollars per share)	$ 0.20	$ 0.24
Granted, non-vested (in shares)	0	0
Granted, weighted average grant date fair value (in dollars per share)
Vested, non-vested (in shares)	(485,999)	(1,284,666)
Vested, weighted average grant date fair value (in dollars per share)	$ 0.19	$ 0.27
Forfeited, non-vested (in shares)	(54,833)	(653,100)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 0.22	$ 0.22
Balance, non-vested (in shares)	53,001	593,833
Balance, non-vested, weighted average grant date fair value (in dollars per share)	$ 0.22	$ 0.20