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	Dec. 31, 2018	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
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