Note 10 - Stockholders' Equity - Option Activity for Stock Option Plans (Details) - USD ($)			12 Months Ended
	Apr. 07, 2019	Dec. 14, 2018	Dec. 31, 2019
Outstanding at January 1, 2019 (in shares)			302,368
Outstanding at January 1, 2019 (in dollars per share)			$ 13.99
Granted, options (in shares)	800,000	214,000	11,450
Granted, weighted average exercise price, options (in dollars per share)	$ 0.65	$ 2.979	$ 4.38
Forfeited/cancelled (in shares)			(22,011)
Forfeited/cancelled, weighted average exercise price, options (in dollars per share)			$ 9.42
Outstanding, options (in shares)			291,807
Outstanding, weighted average exercise price, options (in dollars per share)			$ 13.96
Outstanding, weighted average remaining contractual life, options (Year)			8 years 109 days
Outstanding, aggregate intrinsic value, options			$ 280,000
Vested and Expected to Vest, options (in shares)			224,102
Vested and Expected to Vest, weighted average exercise price, options (in dollars per share)			$ 15.72
Vested and Expected to Vest, weighted average remaining contractual life, options (Year)			8 years 73 days
Vested and Expected to Vest, aggregate intrinsic value, options			$ 203,000
Exercisable, options (in shares)			147,124
Exercisable, weighted average exercise price, options (in dollars per share)			$ 19.79
Exercisable, weighted average remaining contractual life, options (Year)			7 years 328 days
Exercisable, aggregate intrinsic value, options			$ 115,000