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Note 11 - Capital Stock (Details Textual) - USD ($)			2 Months Ended	9 Months Ended
	May 15, 2018	Mar. 06, 2018	May 15, 2018	Sep. 30, 2018	Sep. 30, 2017	May 04, 2018	Feb. 28, 2018	Feb. 22, 2018	Dec. 31, 2017
Proceeds from Issuance of Common Stock				$ 150,000,000	$ 52,467,336
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 A [Member]
Sale of Stock, Value, Available to Issue								$ 150,000,000
Sale of Stock, Price Per Share								$ 23.30
Share Price								$ 23.29
Stock Issued During Period, Shares, New Issues	3,137,768	3,300,000
Proceeds from Issuance of Common Stock	$ 73,110,000	$ 76,890,000	$ 150,000,000
Common Stock, Shares Authorized				38,838,884		38,838,884			38,838,884
Class of Warrant or Right, Outstanding				784
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				1,177,929
Proceeds from Issuance of Common Stock				$ 26,696,400
Compensation, Percentage of Common Stock Sales							3.00%
Proceeds from Issuance of Common Stock, Net				$ 25,141,100
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

X

- Definition

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.

+ References

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The maximum agreed upon value of stock available for issuance.

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Number of warrants or rights outstanding.

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-SubTopic 10
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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Price of a single share of a number of saleable stocks of a company.

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