Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($)			1 Months Ended		2 Months Ended		12 Months Ended		204 Months Ended
	May 25, 2017	Jan. 01, 2002	Mar. 31, 2018	May 31, 2017	Feb. 28, 2019	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Mar. 17, 2019	Jan. 01, 2019	Nov. 30, 2018	May 31, 1988
Net Income (Loss) Attributable to Parent, Total							$ (26,273,000)	$ (33,864,000)
Working Capital						$ 8,900,000	8,900,000		$ 8,900,000
Net Cash Provided by (Used in) Operating Activities, Total							(12,193,000)	(10,466,000)
Proceeds from Issuance of Common Stock							$ 15,503,000
Debt Instrument, Convertible, Conversion Price	$ 6.75					$ 6.75	$ 6.75		$ 6.75
Long-term Debt, Total						$ 155,494,000	$ 155,494,000		$ 155,494,000
Debt Instrument, Maturity Date, Percentage of Conversion Rate,	120.00%
Share-based Compensation, Total							$ 473,000	$ 2,304,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount							0
Weighted Average Number Diluted Shares Outstanding Adjustment, Total							11,398,000	10,894,000
Goodwill, Ending Balance						$ 3,813,000	$ 3,813,000	$ 3,813,000	3,813,000				$ 7,006,000
Goodwill Amortized Portion		$ 3,193,000
Goodwill, Impairment Loss									$ 0
Percentage of Future Quarterly Interest Payments						25.00%	25.00%		25.00%
Interest Payments in Stock							$ 1,290,000
Debt Conversion, Original Debt, Amount							$ 2,800,000
Stock Issued During Period, Shares, Conversion of Convertible Securities							376,463
Income Taxes Paid							$ 6,000	4,000
General and Administrative Expense [Member]
Share-based Compensation, Total							500,000	$ 2,300,000
124-mile Extension Possible for Northern Pipeline, Available for Purchase [Member]
Required Payment to Acquire Property Available for Purchase, Due End of Fiscal Year						$ 18,000,000	$ 18,000,000		$ 18,000,000
Land, Buildings and Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life							10 years
Land, Buildings and Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life							45 years
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life							5 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life							15 years
Subsequent Event [Member]
Convertible Debt, Option Agreements, Percentage										95.00%
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset											$ 151,000
Operating Lease, Liability, Total											$ 100,000
Senior Secured Debt [Member]
Debt Instrument, Face Amount				$ 60,000,000
Debt Instrument, Additional Amount after Refinance	$ 15,000,000			15,000,000
Long-term Debt, Total						66,100,000	$ 66,100,000		66,100,000
Debt Instrument, Maturity Date, Percentage of Conversion Rate,							120.00%
Debt Instrument, Maturity Date, Minimum Principal Outstanding Amount	10,000,000					10,000,000	$ 10,000,000		10,000,000
Prior Senior Secured Debt [Member]
Extinguishment of Debt, Amount	$ 45,000,000			$ 45,000,000
2020 Convertible Senior Notes [Member]
Long-term Debt, Maturities, Repayments of Principal and Interest in Year Two						$ 79,600,000	$ 79,600,000		$ 79,600,000
Debt Instrument, Interest Rate, Stated Percentage	7.00%					7.00%	7.00%		7.00%
Debt Instrument, Convertible, Conversion Price						$ 6.75	$ 6.75		$ 6.75
November 2018 ATM Offering [Member]
At Market Issuance Sales Agreement, Maximum Aggregate Offering Price			$ 15,000,000									$ 25,000,000
Stock Issued During Period, Shares, New Issues			1,159,718			97,106
Proceeds from Issuance of Common Stock, Gross			$ 15,000,000			$ 1,050,000
Proceeds from Issuance of Common Stock			$ 14,600,000			$ 900,000
November 2018 ATM Offering [Member] | Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues					782,814
Proceeds from Issuance of Common Stock, Gross					$ 8,080,000
Proceeds from Issuance of Common Stock					$ 7,920,000