Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Note 13 - Injection Wells Suspension (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2014
Number of Suspended Saltwater Injection Wells				2
Property, Plant and Equipment, Net		$ 43,721	$ 43,971
Wells and Related Equipment and Facilities [Member]
Property, Plant and Equipment, Net			$ 4,300
Wells and Related Equipment and Facilities [Member] \| Scenario, Forecast [Member] \| Maximum [Member]
Tangible Asset Impairment Charges	$ 4,000