Significant Accounting Policies (Intangibles) (Details) - CO2 Purchase Contract - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible asset value	$ 37,848	$ 37,848
Accumulated amortization	(13,074)	(10,645)
Net book value	$ 24,774	$ 27,203

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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-Publisher FASB
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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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