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Related-Party Transactions - Additional Information (Details) - USD ($) $ in Thousands | Aug. 11, 2021 | Jun. 30, 2022 | Sep. 30, 2021
--- | --- | --- | ---
Related Party Transaction [Line Items] |  |  |
Borrowing from related parties |  | $ 0 | $ 50,000
Provision for receivables from related parties |  | $ 0 | $ 0
Common Class B-1 |  |  |
Related Party Transaction [Line Items] |  |  |
Common stock, shares outstanding (in shares) |  | 58,586,695 |
Class A common stock |  |  |
Related Party Transaction [Line Items] |  |  |
Common stock, shares outstanding (in shares) |  | 114,112,407 |
Affiliated Entity | AES Grid Stability |  |  |
Related Party Transaction [Line Items] |  |  |
Borrowing from related parties | $ 25,000 |  |
Subordinated promissory note, annual interest percentage | 2.86% |  |
Affiliated Entity | AES Grid Stability | Common Class B-1 |  |  |
Related Party Transaction [Line Items] |  |  |
Common stock, shares outstanding (in shares) |  | 58,586,695 |
Affiliated Entity | Siemens Industry |  |  |
Related Party Transaction [Line Items] |  |  |
Borrowing from related parties | $ 25,000 |  |
Subordinated promissory note, annual interest percentage | 2.86% |  |
Affiliated Entity | Siemens Industry | Class A common stock |  |  |
Related Party Transaction [Line Items] |  |  |
Common stock, shares outstanding (in shares) |  | 58,586,695 |

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