Fair Value Measurements - Additional Information (Detail) |
Mar. 31, 2025 |
Mar. 31, 2024 |
|---|---|---|
| Foreign bonds [Member] | Japanese bonds [Member] | ||
| Statements [Line Items] | ||
| Percentage of total investment in bonds | 32.00% | 29.00% |
| Foreign bonds [Member] | US European and other bonds [Member] | ||
| Statements [Line Items] | ||
| Percentage of total investment in bonds | 68.00% | 71.00% |
| Other equity securities [Member] | Listed stocks on the Japanese stock markets [Member] | ||
| Statements [Line Items] | ||
| Percentage of total investment in stocks | 79.00% | 85.00% |