Commitments and contingencies - Schedule Of Balance Sheet Information Related to Operating Lease (Detail) - JPY (¥) ¥ in Millions |
Mar. 31, 2026 |
Mar. 31, 2025 |
|---|---|---|
| Commitments and Contingencies Disclosure [Abstract] | ||
| Right-of-use assets | ¥ 483,068 | ¥ 474,361 |
| Lease liabilities | ¥ 521,941 | ¥ 502,997 |
| Operating Lease, Liability, Statement of Financial Position [Extensible List] | Other liabilities (Note 12) | Other liabilities (Note 12) |
| Weighted average: | ||
| Remaining lease term | 12 years 7 months 6 days | 13 years 6 months |
| Discount rate | 1.35% | 1.06% |