The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid within one year of the balance sheet date.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 7

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Commitments and Contingencies (Details 2) (Molycorp Mountain Pass facility, USD $) In Millions, unless otherwise specified		12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011 Potential Environmental Obligations liner	Mar. 31, 2012 Project Phoenix Phase 1 and Project Phoenix Phase 2
Plant Modernization and Expansion Commitments
Estimated future payments for commitments due in one year			$ 336.0
Estimated future payments for commitments due in one to two years	384.7
Potential Environmental Obligations
Number of liner defects		3
Remediation costs, low estimate		2.4
Remediation costs, high estimate		$ 4.6