Segment and geographic information - Business segments' results (Parenthetical) (Detail) - JPY (¥) ¥ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Net gain on trading	¥ 160,905	¥ 91,142	¥ 302,823	¥ 143,136
Non-interest expenses - Other	¥ 33,274	¥ 76,873	¥ 78,230	125,087
US Client [Member]
Segment Reporting Information [Line Items]
Losses arising from transactions included in Non-interest revenue and Non-interest expense				65,362
Net gain on trading				(56,073)
Non-interest expenses - Other				¥ 9,289

Amount of gain (loss) resulting from the difference between the acquisition price and the selling price or fair value of trading assets and trading liabilities, conducted separately from customer trading activities. Includes, but is not limited to, changes in fair value of trading assets and trading liabilities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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