Financial Risks - Additional Information (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Statement [Line Items] | ||
| Impact on other comprehensive income, before tax effect | ¥ (225,875) | ¥ (235,959) |
| Unused commitment lines | 6,753,849 | 5,485,781 |
| Credit limits other than commitment lines | ¥ 88,500 | ¥ 53,000 |
| Equity price risk [member] | Trading equity securities [member] | ||
| Statement [Line Items] | ||
| Percentage of equity financial assets changes | 10.00% | 10.00% |
| Impact on other comprehensive income, before tax effect | ¥ 331,161 | ¥ 305,475 |
| Interest rate, measurement input [Member] | ||
| Statement [Line Items] | ||
| Percentage of reasonably possible increase in unobservable input, assets | 1.00% | 1.00% |