Financial Risks - Additional Information (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Statement [Line Items] | ||
| Impact on other comprehensive income, before tax effect | ¥ (235,959) | ¥ (221,420) |
| Unused commitment lines | 5,503,689 | 5,507,761 |
| Credit limits and other non contractual credit facilities | ¥ 53,000 | ¥ 47,000 |
| 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 | ¥ 305,475 | ¥ 364,120 |
| Interest rate, measurement input [Member] | ||
| Statement [Line Items] | ||
| Percentage of reasonably possible increase in unobservable input, assets | 1.00% | 1.00% |