Collateralized transactions - Assets owned, pledged as collateral ,primarily to stock exchanges and clearing organizations (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2023	Mar. 31, 2023
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading assets		¥ 4,539,219	¥ 3,817,779
Non-trading debt securities	[1]	100,457	106,319
Investments in and advances to affiliated companies	[2]	14,673	14,023
Equities and convertible securities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading assets		222,349	194,486
Government and government agency securities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading assets		1,513,312	1,017,843
Bank and corporate debt securities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading assets		49,736	55,532
Residential mortgage-backed securities ("RMBS") [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading assets		2,704,642	2,527,124
Collateralized debt obligations ("CDOs") and other [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading assets	[3]	11,375	12,383
Investment trust funds and other [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading assets		¥ 37,805	¥ 10,411

[1] Non-trading debt securities are primarily Japanese municipal securities issued by prefectures or ordinance-designated city.

[2] Investments in and advances to affiliated companies comprise shares in Nomura Research Institute, Ltd.

[3] Includes CLOs and ABS such as those secured on credit card loans, auto loans and student loans.