Investments - Narrative (Details) - USD ($) $ in Millions |
Jun. 30, 2025 |
Sep. 30, 2024 |
|---|---|---|
| Investments, Debt and Equity Securities [Abstract] | ||
| Equity securities without readily determinable fair value, upward price adjustment, cumulative amount | $ 23.0 | $ 23.0 |
| Equity securities without readily determinable fair value, downward price adjustment, cumulative amount | $ 11.0 | $ 7.0 |