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Note 12 - Capital Stock (Details Textual) - USD ($)					1 Months Ended		2 Months Ended	12 Months Ended
	May 15, 2018	Mar. 06, 2018	Jul. 18, 2017	Jun. 22, 2017	Jul. 18, 2017	Jul. 18, 2017	May 15, 2018	Dec. 31, 2018	Dec. 31, 2017	Aug. 03, 2018	May 04, 2018	Feb. 28, 2018	Feb. 22, 2018	Jun. 15, 2017
Proceeds from Issuance of Common Stock								$ 150,000,000	$ 52,467,336
Payments of Stock Issuance Costs								$ 1,614,555	$ 961,953
Common Stock, Shares Authorized											40,000,000
Preferred Stock, Shares Authorized								1,000,000	1,000,000		1,000,000
Class of Warrant or Right, Outstanding								105,556	105,556
Common Class B [Member]
Common Stock, Shares Authorized								1,161,116	1,161,116		1,161,116
Class of Warrant or Right, Outstanding								104,772
Class of Warrant or Right, Number of Securities Called by Warrants or Rights										784
Common Class B [Member] | Prospectus Offering [Member]
Shares Authorized to be Issued														6,538,462
Sale of Stock, Price Per Share														$ 13
Common Class B [Member] | Over-Allotment Option [Member] | Maximum [Member]
Shares Authorized to be Issued														980,769
Common Class A [Member]
Sale of Stock, Price Per Share													$ 23.30
Stock Issued During Period, Shares, New Issues	3,137,768	3,300,000		7,113,462
Proceeds from Issuance of Common Stock	$ 73,110,000	$ 76,890,000		$ 88,139,834			$ 150,000,000
Proceeds from Issuance of Common Stock, Net			$ 4,254,229			$ 91,432,110
Payments of Stock Issuance Costs			$ 961,953
Sale of Stock, Value, Available to Issue													$ 150,000,000
Share Price													$ 23.29
Common Stock, Shares Authorized								38,838,884	38,838,884		38,838,884
Class of Warrant or Right, Outstanding								784
Common Class A [Member] | Two Major Controlling Directors [Member]
Stock Issued During Period, Shares, New Issues				3,653,846
Sale of Stock, Consideration Received on Transaction				$ 46,312,498
Common Class A [Member] | Officer and Director [Member]
Stock Issued During Period, Shares, New Issues				509,085
Sale of Stock, Consideration Received on Transaction				$ 6,154,838
Common Class A [Member] | Prospectus Offering [Member]
Stock Issued During Period, Shares, New Issues				6,538,462
Common Class A [Member] | Over-Allotment Option [Member]
Stock Issued During Period, Shares, New Issues			351,880	575,000	926,880
Common Class A [Member] | Shelf Registration [Member]
Sale of Stock, Shelf Registration, Value, Available to Issue												$ 200,000,000
Sale of Stock, Shelf Registration, Value, Incremental Amount Available to Issue												$ 50,000,000
Common Class A [Member] | Shelf Registration [Member] | Cowen and Company LLC [Member]
Stock Issued During Period, Shares, New Issues								1,199,229
Proceeds from Issuance of Common Stock								$ 27,245,682
Proceeds from Issuance of Common Stock, Net								$ 26,428,311
Compensation, Percentage of Common Stock Sales												3.00%

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The percentage amount given to the seller or agent in regards to the sale of common stock they facilitate, measured as a percentage of the common stock sold.

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