Annual report pursuant to Section 13 and 15(d)

Note 10 - Shareholders' Equity (Details Textual)

v3.19.1
Note 10 - Shareholders' Equity (Details Textual)
 1 Months Ended 12 Months Ended
Dec. 11, 2018
USD ($)
$ / shares
shares
Mar. 29, 2018
USD ($)
$ / shares
shares
Dec. 18, 2017
USD ($)
$ / shares
shares
Apr. 17, 2017
USD ($)
$ / shares
shares
Feb. 29, 2016
USD ($)
shares
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
USD ($)
shares
Feb. 29, 2016
$ / shares
shares
Rights, Threshold Trigger to be Exercisable, Percent of Common Stock Outstanding Owned by Individual           20.00%    
Rights, Exercisable, Percent of Discount to Market Price           50.00%    
Proceeds from Issuance of Common Stock | $           $ 14,726,000 $ 2,917,000  
Stock Issued During Period, Shares, Exercise of Common Stock Warrants           128,594 134,079  
Proceeds from Warrant Exercises | $           $ 607,000 $ 615,000  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period           16,954 3,000  
Proceeds from Stock Options Exercised | $           $ 43,000 $ 7,000  
Warrants Issued With IPO [Member]                
Warrants Issued, Cash Consideration | $ $ 50,000              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 205,000              
Warrants and Rights Outstanding, Percent of Outstanding Common Stock Outstanding Called by Warrants 5.00%              
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares $ 4.80              
Class of Warrants or Rights, Percent of IPO Price Per Share of Exercise Price of Warrants 120.00%              
Warrants and Rights Outstanding, Term 5 years              
Warrants Issued in Private Placement [Member]                
Class of Warrant or Right, Exercise Price of Warrants or Rights | (per share)   $ 7 $ 7 $ 4.60       $ 5
Class of Warrant or Right, Issued During Period   661,482            
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right   1 1 1       1
Warrants and Rights Outstanding, Expiration, Stock Price Trigger | $ / shares   $ 12 $ 12 $ 6        
Stock Issued During Period, Shares, Exercise of Common Stock Warrants             131,578  
Proceeds from Warrant Exercises | $         $ 281,000      
Warrants and Rights, Threshold Consecutive Trading Days     21 10        
Compensation Warrants [Member]                
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares   $ 4.90            
Warrants and Rights Outstanding, Term   2 years            
Class of Warrant or Right, Issued During Period   80,510            
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right   1            
IPO [Member]                
Stock Issued During Period, Shares, New Issues 4,100,000              
Shares Issued, Price Per Share | $ / shares $ 4              
Proceeds from Issuance of Common Stock | $ $ 16,400,000              
Proceeds from Issuance of Common Stock, Net | $ $ 14,700,000              
Private Placement [Member]                
Shares Issued, Price Per Share | $ / shares   $ 4.90            
Units Issued During Period, Units, New Issues   1,322,965 181,220 526,316 234,375      
Proceeds From Issuance of Units | $   $ 6,300,000 $ 944,000 $ 2,000,000        
Units, Number of Common Shares Per Unit   1 1 1       1
Units, Number of Common Share Purchase Warrant Per Unit   0.5 0.5 0.5       0.5
Payment for Finders Fee | $   $ 384,000            
Units Issued, Price Per Unit | $ / shares     $ 5.20 $ 3.80        
Proceeds From Issuance of Units, Net | $     $ 934,000 $ 1,983,000