Commitments and Contingencies - Additional Information (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | ||
|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Commitments And Contingencies Disclosure [Line Items] | |||
| Carrying amount of guarantees and similar obligations | ¥ 1,845,000 | ¥ 615,000 | |
| Carrying amounts of derivatives that are deemed to guarantees | 1,815,000 | 583,000 | |
| Allowance for credit losses on off-balance-sheet instruments | (500) | 27,080 | ¥ 9,585 |
| Other Liabilities | |||
| Commitments And Contingencies Disclosure [Line Items] | |||
| Allowance for credit losses on off-balance-sheet instruments | ¥ 116,000 | ¥ 115,000 | |