CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Current assets
Cash and cash equivalents	$ 260,336	$ 1,166,011
Short-term investments	1,077,575	664,275
Total cash, cash equivalents and short-term investments	1,337,911	1,830,286
Trade accounts receivable, net of allowance for credit losses of $0 and $0, respectively	64,074	14,642
Other receivables	57,638	132,042
Inventories	176,139	171,560
Prepaid expenses and other current assets	19,082	17,271
Total current assets	1,654,844	2,165,801
Non-current assets
Property, plant and equipment, net	1,757,949	1,369,817
Inventories	117,032	80,539
Price protection agreement upfront asset, net	176,759	209,668
Other non-current assets	79,903	38,335
Total non-current assets	2,131,643	1,698,359
Total assets	3,786,487	3,864,160
Current liabilities
Accounts and construction payable	80,184	36,655
Accrued liabilities	109,650	95,086
Current portion of long-term debt	0	67,411
Deferred revenue	32,304	74,301
Other current liabilities	22,849	25,596
Total current liabilities	244,987	299,049
Non-current liabilities
Long-term debt, net of current portion	936,253	931,330
Deferred revenue	88,121	83,889
Deferred government grant	26,410	22,101
Deferred investment tax credit	32,411	26,860
Deferred income taxes	23,614	51,558
Other non-current liabilities	70,981	57,005
Total non-current liabilities	1,177,790	1,172,743
Total liabilities	1,422,777	1,471,792
Commitments and contingencies (Note 11)
Redeemable preferred stock	413,611	413,611
Stockholders’ equity:
Preferred stock, undesignated ($0.0001 par value, 49,600,000 shares authorized as of September 30, 2026, and December 31, 2025, respectively, zero issued and outstanding in either period)	0	0
Common stock ($0.0001 par value, 450,000,000 shares authorized, 193,484,771 and 192,607,429 shares issued, and 178,234,989 and 177,357,647 shares outstanding, as of September 30, 2026, and December 31, 2025, respectively)	19	19
Additional paid-in capital	1,992,468	1,970,970
Retained earnings	185,454	234,428
Accumulated other comprehensive income (loss)	(795)	387
Treasury stock, at cost, 15,249,782 shares for both periods	(227,047)	(227,047)
Total stockholders’ equity	1,950,099	1,978,757
Total liabilities, redeemable preferred stock and stockholders’ equity	$ 3,786,487	$ 3,864,160

Price Protection Agreement, Upfront Asset, Net

No definition available.

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Namespace Prefix:	mp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).