Derivative instruments and hedging activities - Additional information (Detail) - JPY (¥) ¥ in Billions	Mar. 31, 2023	Mar. 31, 2022
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liability position with credit-risk-related contingent features	¥ 574	¥ 638
Collateral pledged for derivative instruments with credit-risk-related contingent features that are in a liability position	403	421
Additional collateral required to be posted, aggregate fair value	¥ 11	¥ 1

Amount of collateral pledged for the derivative instruments with credit-risk-related contingent features that are in a liability position.

No definition available.

+ Details

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Namespace Prefix:	nmr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position.

+ References

No definition available.

+ Details

Name:	nmr_FairValueOfDerivativeLiabilityCreditRiskRelatedToContingentFeatures
Namespace Prefix:	nmr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624258-113959

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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