Asset Retirement Obligation (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Asset retirement obligation activity
Balance at beginning of period	$ 15,541,000	$ 12,471,000
Obligations settled	(2,954,000)	(1,030,000)
Accretion expense	1,299,000	955,000
Revisions in estimated cash flows	7,872,000	2,508,000
Loss on settlement	367,000	637,000
Balance at end of period	22,125,000	15,541,000	12,471,000
Asset Retirement Obligation [Abstract]
Asset retirement obligation, current	3,500,000	400,000
Depreciation expense	2,000,000	1,000,000	1,100,000
Financial assurance requirement satisfied with surety bonds	28,700,000
Molycorp Mountain Pass
Asset retirement obligation activity
Revisions in estimated cash flows	3,800,000
Demolition and Reclamation of the Old Mill and Mineral Recovery Areas at the Molycorp Mountain Pass Facility
Asset retirement obligation activity
Revisions in estimated cash flows	$ 4,100,000

Asset Retirement Obligation, Depreciation Expense

No definition available.

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- Definition

Represents the loss on settlement of liabilities related to asset retirement obligation.

+ References

No definition available.

+ Details

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- Definition

The amount of surety bonds with governmental agencies to secure reclamation obligations.

+ References

No definition available.

+ Details

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- Definition

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

-Glossary Asset Retirement Obligation

-URI http://asc.fasb.org/extlink&oid=6505190

+ Details

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- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

+ Details

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- Definition

Current portion of 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

+ Details

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- Definition

Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

+ References

+ Details

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- Definition

Amount of the Increase or Decrease in the amount of the asset retirement obligation during the current period for changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

+ Details

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