Retirement Benefits - Sensitivity Analyses of Effect of Changes in Key Assumptions on Defined Benefit Obligations (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Discount rates [member] | ||
| Disclosure of sensitivity analysis for actuarial assumptions [Line Items] | ||
| Percentage increase in assumption | 0.50% | 0.50% |
| Increase/(decrease) in defined benefit obligations due to increase in assumption | ¥ (32,112) | ¥ (40,637) |
| Percentage decrease in assumption | 0.50% | 0.50% |
| Increase/(decrease) in defined benefit obligations due to decrease in assumption | ¥ 35,458 | ¥ 45,208 |
| Average life expectancy at age 60 [member] | ||
| Disclosure of sensitivity analysis for actuarial assumptions [Line Items] | ||
| Year increase in assumption | 1 year | 1 year |
| Increase/(decrease) in defined benefit obligations due to increase in assumption | ¥ 18,325 | ¥ 23,391 |