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Note 7 - Shareholders' Equity (Details Textual) - USD ($) |  |  |  | 1 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 22, 2018 | Oct. 23, 2017 | Oct. 13, 2017 | Sep. 30, 2016 | Jun. 30, 2018 | Mar. 31, 2019 | Apr. 21, 2018 | Mar. 31, 2013
Common Stock, Shares Authorized |  |  |  |  | 30,000,000 | 30,000,000 |  |
Preferred Stock, Shares Authorized |  |  |  |  |  | 15,000,000 |  |
Common Stock, Shares, Outstanding, Ending Balance |  |  |  |  | 6,153,266 | 6,357,113 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance |  |  |  |  |  | 0 |  |
Preferred Stock, Shares Issued, Total |  |  |  |  |  | 0 |  |
Common Stock, Par or Stated Value Per Share |  |  |  | $ 0.01 | $ 0.01 | $ 0.01 |  |
Common Stock Issued in Connection with Warrants Exercised [Member] |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercised During Period |  |  |  |  | 404,923 |  |  |
Private Placement [Member] | March 2013 Warrant Holders [Member] |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share |  |  | $ 0.01 |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  | $ 10 |  |  |  |  |
Class of Warrant or Right, Exercised During Period |  |  | 124,999 |  |  |  |  |
Proceeds from Warrant Exercises |  |  | $ 1,200,000 |  |  |  |  |
Class of Warrant or Right, Reduced Exercise Price of Warrants or Rights |  |  | $ 9.50 |  |  |  |  |
Private Placement [Member] | Certain Purchasers [Member] |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share |  | $ 0.01 |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues |  | 553,672 |  |  |  |  |  |
Shares Issued, Price Per Share |  | $ 19 |  |  |  |  |  |
Proceeds from Issuance of Private Placement |  | $ 10,500,000 |  |  |  |  |  |
Proceeds from Issuance of Private Placement, Net of Issuance Costs |  | $ 10,000,000 |  |  |  |  |  |
Private Placement Fee, Percentage |  | 6.50% |  |  |  |  |  |
Private Placement Fee, Reduced Percentage |  | 3.25% |  |  |  |  |  |
Payments of Stock Issuance Costs |  | $ 500,000 |  |  |  |  |  |
Juneau Exploration L.P. [Member] | Private Placement [Member] |  |  |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues |  | 13,200 |  |  |  |  |  |
Stock Issued During Period, Value, New Issues |  | $ 250,800 |  |  |  |  |  |
March 2013 Warrant [Member] |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  | $ 9 |  |  |  | $ 10
Class of Warrant or Right, Exercised During Period |  |  |  | 587,500 | 580,999 |  |  |
Proceeds from Warrant Exercises |  |  |  | $ 5,300,000 |  |  |  |
Stock Issued During Period, Value, Warrants Exercised |  |  |  |  | $ 2,300,000 |  |  |
March 2013 Warrant [Member] | Entities Controlled by CEO [Member] |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercised During Period |  |  |  | 83,334 |  |  |  |
Rights to Purchase Series A Junior Preferred Stock [Member] |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  |  |  | $ 80 |  |
Rights Agreement Term Extension Period | 1 year |  |  |  |  |  |  |
Beneficial Ownership Required for Rights to Be Exercisable | 15.00% |  |  |  |  |  | 23.00% |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights |  |  |  |  |  | 0.01 |  |
Class of Warrant or Right, Distributed for Each Share of Common Stock |  |  |  |  |  | 1 |  |
Restricted Stock [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance |  |  |  |  |  | 456,666 |  |

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