Note 1 - Basis of Presentation (Details Textual) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Mar. 31, 2018	May 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net Income (Loss) Attributable to Parent, Total			$ (6,032)	$ (13,570)	$ (12,003)	$ (20,797)
Working Capital			$ 17,700		17,700
Net Cash Provided by (Used in) Operating Activities, Total					(6,419)	(4,867)
Proceeds from Issuance of Common Stock					$ 14,581
Percentage of Future Quarterly Interest Payments			25.00%		25.00%
Interest Payments in Stock					$ 630
Debt Conversion, Original Debt, Amount					$ 1,960
Stock Issued During Period, Shares, Conversion of Convertible Securities					257,923
124-mile Extension Possible for Northern Pipeline, Available for Purchase [Member]
Required Payment to Acquire Property Available for Purchase, Due End of Fiscal Year			$ 20,000		$ 20,000
Senior Secured Debt [Member]
Debt Instrument, Fee Amount		$ 60,000
Debt Instrument, Additional Amount after Refinance		15,000
Prior Senior Secured Debt [Member]
Extinguishment of Debt, Amount		$ 45,000
At Market Issuance Sales Agreement [Member]
At Market Issuance Sales Agreement, Maximum Aggregate Offering Price	$ 15,000
Stock Issued During Period, Shares, New Issues	1,159,718
Proceeds from Issuance of Common Stock, Gross	$ 15,000
Proceeds from Issuance of Common Stock	$ 14,600