XML 28 R15.htm IDEA: XBRL DOCUMENT
v3.24.3

ASSET RETIREMENT AND ENVIRONMENTAL OBLIGATIONS | 9 Months Ended
--- | ---
Sep. 30, 2024
Asset Retirement Obligation Disclosure [Abstract] |
ASSET RETIREMENT AND ENVIRONMENTAL OBLIGATIONS | ASSET RETIREMENT AND ENVIRONMENTAL OBLIGATIONS Asset Retirement Obligations The Company estimates asset retirement obligations based on the requirements to reclaim certain land areas associated with mineral extraction activities and certain related facilities at Mountain Pass. Minor reclamation activities related to discrete portions of the Company’s operations are ongoing. As of September 30, 2024, the Company estimated a significant portion of the cash outflows for major reclamation activities including the retirement of Mountain Pass will be incurred beginning in 2056. As of September 30, 2024, the credit-adjusted risk-free rate ranged between 6.5% and 12.0% depending on the timing of expected settlement and when the increment was recognized. There were no significant increments or decrements for the three and nine months ended September 30, 2024 and 2023. The balance as of both September 30, 2024 and December 31, 2023, included current portions of $0.2 million, which are included in “Other current liabilities” within the Company’s unaudited Condensed Consolidated Balance Sheets. The total estimated future undiscounted cash flows required to satisfy the Company’s asset retirement obligations were $52.5 million and $50.2 million as of September 30, 2024, and December 31, 2023, respectively. Environmental Obligations The Company has certain environmental monitoring and remediation obligations related to the monitoring of groundwater contamination. The Company engaged an environmental consultant to develop a remediation plan and remediation cost projections based upon that plan. Utilizing the consultant’s plan, the Company developed an estimate of future cash payments for the environmental obligations. As of September 30, 2024, the Company estimated the cash outflows related to these environmental activities will be incurred annually over the next 23 years. The Company’s environmental obligations are measured at the expected value of future cash outflows discounted to their present value using a discount rate of 2.93%. There were no significant changes in the estimated remaining remediation costs for the three and nine months ended September 30, 2024 and 2023. The total estimated aggregate undiscounted cost of $26.3 million and $26.7 million as of September 30, 2024, and December 31, 2023, respectively, principally related to water monitoring activities required by state and local agencies. Based on the Company’s estimate of the cost and timing and the assumption that payments are considered to be fixed and reliably determinable, the Company has discounted the liability. The balance as of both September 30, 2024, and December 31, 2023, included current portions of $0.5 million, which are included in “Other current liabilities” within the Company’s unaudited Condensed Consolidated Balance Sheets. Financial Assurances The Company is required to provide certain government agencies with financial assurances relating to closure and reclamation obligations. As of September 30, 2024, and December 31, 2023, the Company had financial assurance requirements of $45.5 million and $45.4 million, respectively, which were satisfied with surety bonds placed with applicable California state and regional agencies.

X
- Definition Asset Retirement Obligation And Environmental Loss Contingency Disclosure + References No definition available. + Details
Name: | mp_AssetRetirementObligationAndEnvironmentalLossContingencyDisclosureTextBlock
Namespace Prefix: | mp_
Data Type: | dtr-types1:textBlockItemType
Balance Type: | na
Period Type: | duration

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