Collateralized transactions - Schedule of securities received as collateral (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2022	Mar. 31, 2022
Collateralized Transactions
The fair value of securities received as collateral, securities borrowed as collateral and securities borrowed without collateral where Nomura is permitted by contract or custom to sell or repledge the securities	¥ 60,879	¥ 48,234
The portion of the above that has been sold (as reported within Trading liabilities in the consolidated balance sheets) or repledged	¥ 41,244	¥ 36,146

Fair value of the collateral, or portion thereof, that has been re-pledged, delivered, or otherwise used.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (c)(2)
-URI https://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Name:	us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatHaveBeenResoldOrRepledged
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant