| Fair Value, by Balance Sheet Grouping [Table Text Block] |
| | | September 30, 2025 | |
| | | (in thousands) | |
| | | Level 1 | | | Level 2 | | | Level 3 | | | Total | |
| Assets | | | | | | | | | | | | | | | | |
| Cash Equivalents: | | | | | | | | | | | | | | | | |
| Certificates of deposit (1) | | $ | — | | | $ | 1,704 | | | $ | — | | | $ | 1,704 | |
| Money market funds | | | — | | | | 4,204 | | | | — | | | | 4,204 | |
| U.S. treasury bills | | | — | | | | 187,127 | | | | — | | | | 187,127 | |
| Prepaid expenses and other current assets: | | | | | | | | | | | | | | | | |
| Certificates of deposit (1) | | | — | | | | 339 | | | | — | | | | 339 | |
| Other assets: | | | | | | | | | | | | | | | | |
| Certificates of deposit (1) | | | — | | | | 206 | | | | — | | | | 206 | |
| Total | | $ | — | | | $ | 193,580 | | | $ | — | | | $ | 193,580 | |
| Liabilities: | | | | | | | | | | | | | | | | |
| Accrued expenses and other current liabilities: | | | | | | | | | | | | | | | | |
| Mandatorily redeemable noncontrolling interest (2) | | $ | — | | | $ | — | | | $ | 5,679 | | | $ | 5,679 | |
| Total | | $ | — | | | $ | — | | | $ | 5,679 | | | $ | 5,679 | |
| | | December 31, 2024 | |
| | | (in thousands) | |
| | | Level 1 | | | Level 2 | | | Level 3 | | | Total | |
| Assets | | | | | | | | | | | | | | | | |
| Cash Equivalents: | | | | | | | | | | | | | | | | |
| Certificates of deposit (1) | | $ | — | | | $ | 1,504 | | | $ | — | | | $ | 1,504 | |
| Money market funds | | | — | | | | 4,188 | | | | — | | | | 4,188 | |
| U.S. treasury bills | | | — | | | | 181,210 | | | | — | | | | 181,210 | |
| Prepaid expenses and other current assets: | | | | | | | | | | | | | | | | |
| Certificates of deposit (1) | | | — | | | | 165 | | | | — | | | | 165 | |
| Other assets: | | | | | | | | | | | | | | | | |
| Certificates of deposit (1) | | | — | | | | 39 | | | | — | | | | 39 | |
| Notes receivables (3) | | | — | | | | — | | | | 3,938 | | | | 3,938 | |
| Total | | $ | — | | | $ | 187,106 | | | $ | 3,938 | | | $ | 191,044 | |
| Liabilities: | | | | | | | | | | | | | | | | |
| Other liabilities: | | | | | | | | | | | | | | | | |
| Warrant liabilities (4) | | $ | — | | | $ | 1,861 | | | $ | — | | | $ | 1,861 | |
| Total | | $ | — | | | $ | 1,861 | | | $ | — | | | $ | 1,861 | |
|
| Debt Securities, Available-for-Sale [Table Text Block] |
| | | September 30, 2025 | |
| | | (in thousands) | |
| | | Amortized Cost | | | Fair Value | | | Gross Unrealized Gains | |
| U.S. treasury bills | | $ | 187,106 | | | $ | 187,127 | | | $ | 21 | |
| Total | | $ | 187,106 | | | $ | 187,127 | | | $ | 21 | |
| | | December 31, 2024 | |
| | | (in thousands) | |
| | | Amortized Cost | | | Fair Value | | | Gross Unrealized Losses | |
| U.S. treasury bills | | $ | 181,217 | | | $ | 181,210 | | | $ | (7 | ) |
| Total | | $ | 181,217 | | | $ | 181,210 | | | $ | (7 | ) |
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