Derivative instruments and hedging activities - Concentration of exposures to credit risk in OTC derivatives with financial institutions (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Derivative [Line Items]
Gross fair value of derivative assets	¥ 17,087	¥ 21,190
Financial institutions [Member]
Derivative [Line Items]
Gross fair value of derivative assets	14,731	17,711
Impact of master netting agreements	(12,943)	(15,479)
Impact of collateral	(1,526)	(1,707)
Net exposure to credit risk	¥ 262	¥ 525

Fair value, before effects of master netting arrangements, of a 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. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Balance Type:	debit
Period Type:	instant