Note 11 - Stock Options and Restricted Stock - Summary of the Status of Non-vested Shares (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Balance, non-vested (in shares)	2,531,599	1,659,834
Balance, non-vested, weighted average grant date fair value (in dollars per share)	$ 0.24	$ 0.58
Granted, non-vested (in shares)	0	2,971,600
Granted, weighted average grant date fair value (in dollars per share)		$ 0.19
Vested, non-vested (in shares)	(1,284,666)	(2,003,167)
Vested, weighted average grant date fair value (in dollars per share)	$ 0.27	$ 0.43
Forfeited, non-vested (in shares)	(653,100)	(96,668)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 0.22	$ 0.55
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