Note 4 - Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property, plant and equipment, net	$ 119,918	$ 92,070
Computer Equipment [Member]
Property, plant and equipment, gross	392	164
Furniture and Fixtures [Member]
Property, plant and equipment, gross	472	316
Leasehold Improvements [Member]
Property, plant and equipment, gross	546	420
Excluding Construction in Progress [Member]
Property, plant and equipment, gross	1,410	900
Less: accumulated depreciation	(706)	(542)
Property, plant and equipment, net	704	358
Construction in Progress [Member]
Property, plant and equipment, gross	119,214	91,712
Construction in Progress [Member] \| Rio Grande [Member]
Property, plant and equipment, gross	107,160	80,407
Construction in Progress [Member] \| Rio Bravo [Member]
Property, plant and equipment, gross	$ 12,054	$ 11,305

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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

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