Name:	gmo_AdditionalRestrictedCashAndCashEquivalentsReclamationBondsNoncurrent
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The number of publications prepared by the SEIS process which would disclose additional information to the public related to the selection of appropriate background concentrations to use for dispersion modeling of air pollutants.

No definition available.

Name:	gmo_NumberOfPublicationsInSEISProcess
Namespace Prefix:	gmo_
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This element represents cash and equivalents whose use in whole or in part is restricted for long-term reclamation bonds.

No definition available.

Name:	gmo_RestrictedCashAndCashEquivalentsReclamationBondsNoncurrent
Namespace Prefix:	gmo_
Data Type:	xbrli:monetaryItemType
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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.

No definition available.

Name:	us-gaap_LossContingenciesLineItems
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Amount of a reclamation and mine closing liability that is associated with a legal obligation for the closure and reclamation of a mine including the removal of buildings, equipment, machinery and other physical remnants of mining, closure of tailings impoundments, leach pads and other mine features, and contouring, covering and revegetation of waste rock piles and other disturbed areas.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.Y.Q2)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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Name:	us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis=gmo_MountHopeProjectMember
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Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_FinancialGuaranteeMember
Namespace Prefix:
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