Note 15 - Subsequent Events (Details Textual) - USD ($)	1 Months Ended	6 Months Ended
	Aug. 14, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 1.95	$ 1.48	$ 0.50	$ 2.55
Proceeds from Warrant Exercises		$ 949,012
First Warrants Exercised Subsequent to June 30, 2020 [Member] | Subsequent Event [Member]
Stock Issued During Period Shares, Warrants Exercised (in shares)	37,500
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 0.50
Proceeds from Warrant Exercises	$ 18,750
Second Warrants Exercised Subsequent to June 30, 2020 [Member] | Subsequent Event [Member]
Stock Issued During Period Shares, Warrants Exercised (in shares)	15,000
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 1.20
Proceeds from Warrant Exercises	$ 18,000