Fair Value Measurement - Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Carrying Value	$ 617,118	$ 813,266
Carrying Value	1,167,057	2,024,381
May 2025 Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Carrying Value	48,217	48,044
November 2025 Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Carrying Value	317,895	530,096
Equipment financing facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Carrying Value	0	372
Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Carrying Value	713,222	1,361,542
DOE Loan Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Carrying Value	87,723	84,327
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value	1,358,527	2,097,255
Level 3 \| May 2025 Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value	73,165	123,000
Level 3 \| November 2025 Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value	454,543	586,237
Level 3 \| Equipment financing facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value	0	375
Level 3 \| Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value	733,747	1,292,216
Level 3 \| DOE Loan Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value	$ 97,072	$ 95,427

Convertible Notes Payable, Fair Value Disclosure

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- Definition

Long-Term Debt, Including Embedded Derivatives

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- Definition

Preferred Stock at Carrying Value

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Preferred Stock at Fair Value

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Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder.

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- 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.

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Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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