XML 85 R72.htm IDEA: XBRL DOCUMENT
v3.24.3

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Financial assets: |  |
Cash and cash equivalents | $ 284,434 | $ 263,351
Fair Value, Inputs, Level 1 [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 284,434 | 263,351
Short-term investments | 582,056 | 734,493
Restricted cash | 1,160 | 1,637
Fair Value, Inputs, Level 1 [Member] | Convertible Debt [Member] | Convertible Notes due 2026 |  |
Financial liabilities: |  |
Debt fair value | 192,938 | 619,496
Fair Value, Inputs, Level 1 [Member] | Convertible Debt [Member] | Convertible Notes due 2030 |  |
Financial liabilities: |  |
Debt fair value | 823,812 |
Fair Value, Inputs, Level 1 [Member] | Equipment notes |  |
Financial liabilities: |  |
Debt fair value | 0 | 0
Fair Value, Inputs, Level 2 [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 0 | 0
Short-term investments | 0 | 0
Restricted cash | 0 | 0
Fair Value, Inputs, Level 2 [Member] | Convertible Debt [Member] | Convertible Notes due 2026 |  |
Financial liabilities: |  |
Debt fair value | 0 | 0
Fair Value, Inputs, Level 2 [Member] | Convertible Debt [Member] | Convertible Notes due 2030 |  |
Financial liabilities: |  |
Debt fair value | 0 |
Fair Value, Inputs, Level 2 [Member] | Equipment notes |  |
Financial liabilities: |  |
Debt fair value | 3,114 | 4,628
Fair Value, Inputs, Level 3 [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 0 | 0
Short-term investments | 0 | 0
Restricted cash | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Convertible Debt [Member] | Convertible Notes due 2026 |  |
Financial liabilities: |  |
Debt fair value | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Convertible Debt [Member] | Convertible Notes due 2030 |  |
Financial liabilities: |  |
Debt fair value | 0 |
Fair Value, Inputs, Level 3 [Member] | Equipment notes |  |
Financial liabilities: |  |
Debt fair value | 0 | 0
Reported Value Measurement [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 284,434 | 263,351
Short-term investments | 582,056 | 734,493
Restricted cash | 1,160 | 1,637
Reported Value Measurement [Member] | Convertible Debt [Member] | Convertible Notes due 2026 |  |
Financial liabilities: |  |
Debt fair value | 208,362 | 681,980
Reported Value Measurement [Member] | Convertible Debt [Member] | Convertible Notes due 2030 |  |
Financial liabilities: |  |
Debt fair value | 729,272 |
Reported Value Measurement [Member] | Equipment notes |  |
Financial liabilities: |  |
Debt fair value | 3,147 | 4,743
Estimate of Fair Value Measurement [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 284,434 | 263,351
Short-term investments | 582,056 | 734,493
Restricted cash | 1,160 | 1,637
Estimate of Fair Value Measurement [Member] | Convertible Debt [Member] | Convertible Notes due 2026 |  |
Financial liabilities: |  |
Debt fair value | 192,938 | 619,496
Estimate of Fair Value Measurement [Member] | Convertible Debt [Member] | Convertible Notes due 2030 |  |
Financial liabilities: |  |
Debt fair value | 823,812 |
Estimate of Fair Value Measurement [Member] | Equipment notes |  |
Financial liabilities: |  |
Debt fair value | $ 3,114 | $ 4,628

X
- Definition Restricted Cash, Fair Value Disclosure + References No definition available. + Details
Name: | mp_RestrictedCashFairValueDisclosure
Namespace Prefix: | mp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2E -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69B -Publisher FASB -URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69C -Publisher FASB -URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1D -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-10 + Details
Name: | us-gaap_DebtInstrumentFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_ConvertibleDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=mp_ConvertibleNotesDue2026Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=mp_ConvertibleNotesDue2030Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=mp_EquipmentNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |