v3.19.2
Note 11 - Stockholders' Equity (Details Textual) - USD ($)
3 Months Ended 6 Months Ended
May 09, 2019
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Stock Issued During Period, Value, New Issues     $ 7,407,000  
ATM Agreement [Member]        
Aggregate Offering Price, Increase During Period $ 40,000,000      
Stock Issued During Period, Value, New Issues   $ 0   $ 0
Public Offering [Member]        
Aggregate Offering Price, Maximum       $ 46,564,331