Settlement Guarantee Management - Additional Information (Detail) - USD ($) $ in Billions |
12 Months Ended | |
|---|---|---|
Sep. 30, 2024 |
Sep. 30, 2023 |
|
| Settlement Guarantee Management [Abstract] | ||
| Maximum settlement exposure | $ 137.4 | |
| Average daily settlement exposure | 84.3 | |
| Total collateral | $ 7.7 | $ 6.2 |