Investments - Narrative (Details) - USD ($) $ in Millions |
Sep. 30, 2026 |
Sep. 30, 2025 |
|---|---|---|
| Investments, Debt and Equity Securities [Abstract] | ||
| Equity securities without readily determinable fair value, upward price adjustment, cumulative amount | $ 23 | $ 23 |
| Equity securities without readily determinable fair value, downward price adjustment and impairment loss, cumulative amount | $ 17 | $ 10 |