Note 5 - Stockholders' Equity and Common Stock Warrants (Details Textual) - USD ($)	1 Months Ended	3 Months Ended
	Jan. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Stock Issued During Period, Shares, Conversion of Convertible Securities	553,752
Common Stock Dividends, Shares	68,815
Stock Issued During Period, Shares, Make-whole Adjustment	777,895
Dividends, Make-whole Adjustment	$ 8,200,000		$ 8,167,895
Class of Warrant or Rights, Expired		0
Class of Warrant or Right, Exercised		0
Conversion From Series A Preferred Stock to Common Stock [Member]
Conversion of Stock, Shares Issued	1,400,462
Warrants Issued in Connection with the January 2018 Offering [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	1,000,000
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 12
Warrants Issued in Connection with the January 2018 Offering [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 15
Option Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	150,000
Additional Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 12
Class of Warrant or Right, Granted	131,375
Underwriter Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 15
Class of Warrant or Right, Term	5 years
Underwriter Warrants [Member] | Maximum [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	50,000
January 2018 Offering [Member]
Stock Issued During Period, Shares, New Issues	1,000,000
Proceeds from Issuance or Sale of Equity, Total	$ 10,800,000
Stock Issued During Period, Shares, Issued for Services	150,000