Represents the gain loss on contract termination attributable to the Contingently Redeemable Noncontrolling Interest.

No definition available.

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Namespace Prefix:	gmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Parent ownership interest in project.

+ References

No definition available.

+ Details

Name:	gmo_ParentProjectOwnershipPercentage
Namespace Prefix:	gmo_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_IndustrySpecificPoliciesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of Net Income (Loss) attributable to redeemable noncontrolling interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.19)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=gmo_EurekaMolyLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=gmo_EurekaMolyLlcMember
Namespace Prefix:
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Balance Type:
Period Type:

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounting Method (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Feb. 29, 2008
Significant Accounting Policy disclosures
Noncontrolling ownership net loss	$ (75,000)	$ 36,000
Eureka Moly LLC
Significant Accounting Policy disclosures
Noncontrolling ownership net loss	374,000
Gain (loss) on contract termination attributable to CRNCI	$ 75,000
Eureka Moly LLC
Significant Accounting Policy disclosures
Ownership interest (as a percent)			80.00%
Noncontrolling Interest, Ownership Percentage by Parent			80.00%
Ownership interest (as a percent)			20.00%
Eureka Moly LLC \| Eureka Moly LLC
Significant Accounting Policy disclosures
Noncontrolling Interest, Ownership Percentage by Parent	80.00%