Borrowings - Net Carrying Value (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Principal	$ 443,793	$ 395,535
Total borrowings	325,514	316,896
2021 Convertible Note Payable | Convertible Notes
Debt Instrument [Line Items]
Principal	122,868	122,868
Unamortized debt discount	(11,131)	(13,045)
Unamortized debt issuance costs	(1,072)	(1,257)
Embedded conversion feature	260	1,272
Total borrowings	110,925	109,838
DOE Loan Facility
Debt Instrument [Line Items]
Total borrowings	66,215	65,452
DOE Loan Facility | PIK Interest
Debt Instrument [Line Items]
Principal	68,279
Unamortized debt issuance costs	(2,979)
Capitalized PIK Interest	915
Total borrowings	66,215
AFG Convertible Notes | Convertible Notes | Related Party
Debt Instrument [Line Items]
Principal	22,353	22,353
Unamortized debt discount	(1,627)	(1,906)
Unamortized debt issuance costs	(459)	(538)
Embedded conversion feature	27,202	43,124
Total borrowings	$ 47,469	$ 63,033