Derivative instruments and hedging activities - Offsetting of derivatives and related collateral amounts (Parenthetical) (Detail) - JPY (¥) ¥ in Billions	Mar. 31, 2026	Mar. 31, 2025
Derivative Instruments and Hedging Activities [Abstract]
Gross balances of derivative assets, not subject to enforceable master netting arrangements or similar agreements	¥ 1,027	¥ 609
Gross balances of derivative liabilities, not subject to enforceable master netting arrangements or similar agreements	1,206	832
Cash collateral receivables against net derivative liabilities	2,035	1,740
Cash collateral payables against net derivative assets	2,416	2,090
Cash collateral receivables, not being offset against net derivatives	399	343
Cash collateral payables, not being offset against net derivatives	¥ 1,300	¥ 1,043

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

- Definition

Fair value of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

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