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PLANT AND EQUIPMENT AND MINERAL PROPERTIES - Schedule of Summary of Mineral Properties (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Mineral properties	$ 83,539		$ 83,539
Abandonment of mineral properties	0	$ 245
Uranerz ISR properties
Property, Plant and Equipment [Line Items]
Mineral properties	25,974		25,974
Sheep Mountain
Property, Plant and Equipment [Line Items]
Mineral properties	34,183		34,183
Roca Honda
Property, Plant and Equipment [Line Items]
Mineral properties	22,095		22,095
Other
Property, Plant and Equipment [Line Items]
Mineral properties	$ 1,287		$ 1,287

X

- Definition

The adjustment to expense previously capitalized costs of drilling exploratory wells when proved reserves are not found or when the entity obtains information that raises substantial doubt about the economic or operational viability of the project.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 40
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6475089&loc=d3e66625-109467

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 35
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66906256&loc=d3e66150-109466

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 40
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6475089&loc=d3e66584-109467

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6475089&loc=d3e66610-109467

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X

- Definition

Mineral properties, net of adjustments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 25
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=96866604&loc=d3e64895-109465

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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