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COMMITMENTS AND CONTINGENCIES (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Commitments [Line Items]
Asset retirement obligation		$ 17,033	$ 8,573	$ 5,683
White Mesa Mill
Other Commitments [Line Items]
Civil penalties	$ 38
Canyon Project
Other Commitments [Line Items]
Loss contingency, estimate of possible loss		23,120	12,980
Asset retirement obligation		43,000	$ 32,030
Debt instrument, collateral fee		1,760
Mining Properties and Mineral Rights
Other Commitments [Line Items]
Leasing costs due in the next twelve months		$ 1,390

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Civil Penalties

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The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6505190

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Amount of fees associated with providing collateral for the debt instrument.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
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-Section 50
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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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-Publisher FASB
-Name Accounting Standards Codification
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