Commitments, Guarantees and Contingent Liabilities (Amounts Due of Certain Computer Systems Operated and Maintained under Non-cancelable Contracts with Third-party Service Providers) (Detail) - JPY (¥) ¥ in Millions |
Sep. 30, 2026 |
Mar. 31, 2026 |
|---|---|---|
| Commitments and Contingencies Disclosure [Abstract] | ||
| Within one year | ¥ 7,874 | ¥ 7,832 |
| More than one year | 5,150 | 7,553 |
| Total | ¥ 13,024 | ¥ 15,385 |