Investments - Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | ||
|---|---|---|---|
Dec. 31, 2024 |
Dec. 31, 2023 |
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 | 8.0 | $ 7.0 | |
| Change in fair value of investments | $ 0.0 | $ 3.0 | |
| Total net unrealized gain on equity securities | $ 2.0 | ||