XML 79 R56.htm IDEA: XBRL DOCUMENT
v3.22.4

PROPERTY, PLANT AND EQUIPMENT - Additional Information (Details) - USD ($) | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Feb. 28, 2022 | Nov. 30, 2020
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Capitalized expenditures |  | $ 361,200,000 | $ 138,000,000 | $ 26,200,000 |  |
Assets transferred | $ 121,000,000 |  |  |  |  |
Proceeds from government awards used for construction |  | 5,130,000 | 4,382,000 | 0 |  |
Technology investment agreement, stage II optimization contribution | 100,000 | 100,000 |  |  |  | $ 9,600,000
Optimization contribution |  |  |  |  | $ 35,000,000 |
Decrease in property, plant and equipment |  | 10,400,000 | 8,700,000 |  |  |
Decrease in depreciation expense |  | 2,700,000 | 1,100,000 |  |  |
Asset impairment charges |  | 0 | 0 | $ 0 |  |
Assets under construction |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Decrease in property, plant and equipment |  | 6,700,000 | 3,200,000 |  |  |
Buildings and building improvements |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Decrease in property, plant and equipment |  | $ 600,000 | 2,000,000 |  |  |
Machinery and equipment |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |
Assets transferred | $ 115,200,000 |  |  |  |  |
Decrease in property, plant and equipment |  |  | $ 2,400,000 |  |  |

X
- Definition HREE Production Project Agreement, Stage II Optimization Contribution + References No definition available. + Details
Name: | mp_HREEProductionProjectAgreementStageIIOptimizationContribution
Namespace Prefix: | mp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Proceeds From Government Reimbursements For Property, Plant And Equipment + References No definition available. + Details
Name: | mp_ProceedsFromGovernmentReimbursementsForPropertyPlantAndEquipment
Namespace Prefix: | mp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Technology Investment Agreement, Stage II Optimization Contribution + References No definition available. + Details
Name: | mp_TechnologyInvestmentAgreementStageIIOptimizationContribution
Namespace Prefix: | mp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase (decrease) in accumulated depreciation, depletion and amortization of property, plant and equipment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
Name: | us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipmentPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=126905981&loc=d3e2420-110228 + Details
Name: | us-gaap_AssetImpairmentCharges
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of acquisition of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentAdditions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentGrossPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition 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. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of increase (decrease) of physical assets used in the normal conduct of business and not intended for resale, from reclassification, impairment, donation, or changes classified as other. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230 + Details
Name: | us-gaap_PropertyPlantAndEquipmentTransfersAndChanges
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ConstructionInProgressMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_MachineryAndEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |