Trading Account Gains and Losses (Net Trading Gains and Losses) (Parenthetical) (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | ||||
|---|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2024 |
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | |||||
| Gains (losses) recorded in income | ¥ 713,441 | ¥ (518,972) | ¥ (560,806) | ||
| Credit-related contracts | |||||
| Schedule of Trading Securities and Other Trading Assets [Line Items] | |||||
| Gains (losses) recorded in income | [1] | 22,718 | (6,531) | 3,053 | |
| Credit-related contracts | Loans related to credit derivatives | |||||
| Schedule of Trading Securities and Other Trading Assets [Line Items] | |||||
| Gains (losses) recorded in income | ¥ (809) | ¥ (964) | ¥ (952) | ||
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