Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents - Schedule of Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents (Details) - USD ($) $ in Millions |
Mar. 31, 2025 |
Sep. 30, 2024 |
Mar. 31, 2024 |
Sep. 30, 2023 |
|---|---|---|---|---|
| Restricted Cash and Cash Equivalents Items [Line Items] | ||||
| Cash and cash equivalents | $ 11,734 | $ 11,975 | ||
| Cash, cash equivalents, restricted cash and restricted cash equivalents | 19,136 | 19,763 | $ 18,948 | $ 21,990 |
| U.S. litigation escrow | ||||
| Restricted Cash and Cash Equivalents Items [Line Items] | ||||
| Restricted cash and restricted cash equivalents: | 2,926 | 3,089 | ||
| Customer collateral | ||||
| Restricted Cash and Cash Equivalents Items [Line Items] | ||||
| Restricted cash and restricted cash equivalents: | 3,543 | 3,524 | ||
| Prepaid expenses and other current assets | ||||
| Restricted Cash and Cash Equivalents Items [Line Items] | ||||
| Restricted cash and restricted cash equivalents: | $ 933 | $ 1,175 |