Settlement Guarantee Management - Collateral (Detail) - USD ($) $ in Millions |
Jun. 30, 2020 |
Sep. 30, 2019 |
|---|---|---|
| Settlement Guarantee Management [Abstract] | ||
| Restricted cash and restricted cash equivalents | $ 1,759 | $ 1,648 |
| Pledged securities at market value | 281 | 259 |
| Letters of credit | 1,273 | 1,293 |
| Guarantees | 704 | 477 |
| Total | $ 4,017 | $ 3,677 |