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Investments in equity securities including investments in equity securities held for relationship purpose following customary business practices in Japan.

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Net receivables arising from unsettled securities transactions reported within Receivables from other than customers

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Amount of the effect of a change in accounting principle on Deferred tax assets.

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Amount of the effect of a change in accounting principle on Other long-term assets.

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Amount of the effect of a change in accounting principle on Payables to other than customers.

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Reclassification from Compensation and benefits to Other expenses

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The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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Represents the quantification of the effect of adopting the new accounting standard or change in accounting principle expected by the entity to have a significant effect on the entity's financial statements.

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Amount of the effect of a change in accounting principle on operating profit or loss.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Amount of liabilities classified as other.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Summary of accounting policies - Additional information (Detail) ¥ in Millions		12 Months Ended
	Apr. 01, 2018 JPY (¥)	Mar. 31, 2019 JPY (¥)	Mar. 31, 2018 JPY (¥)	Mar. 31, 2017 JPY (¥)	Apr. 01, 2019 JPY (¥)
Accounting Policy [Line Items]
Number of business segments		3
Net receivables arising from unsettled securities transactions		¥ 345,850	¥ 419,161
Depreciation and amortization charges of both owned and capital lease assets		57,924	71,579	¥ 70,928
Investments in equity securities		138,447	150,760
Restricted cash and restricted cash equivalents		473	229	226
Office buildings, land, equipment and facilities		349,365	338,984
Other liabilities		858,867	950,534
Certain cash margin amounts included in Receivables from other than customers [Member]
Accounting Policy [Line Items]
Change in Accounting Policy, Effect of Adoption, Quantification	¥ 237,000
Certain cash margin amounts included in Payables to other than customers [Member]
Accounting Policy [Line Items]
Change in Accounting Policy, Effect of Adoption, Quantification	237,000
Accounting Standards Update 2014-09 [Member]
Accounting Policy [Line Items]
New accounting standards impact on Retained earnings	1,564
New accounting standards impact on Payables to other than customers	517
New accounting standards impact on Other long-term assets	1,750
New accounting standards impact on Deferred tax assets	¥ 703
Accounting Standards Update 2016-18 [Member]
Accounting Policy [Line Items]
Restricted cash and restricted cash equivalents		473
Accounting Standards Update 2017-07 [Member]
Accounting Policy [Line Items]
Reclassification from Compensation and benefits to Other expenses		1,020
Accounting Standards Update 2016-02 [Member]
Accounting Policy [Line Items]
Office buildings, land, equipment and facilities					¥ 169,277
Other liabilities					163,685
Retained earnings					¥ 5,592
Listed equity [Member]
Accounting Policy [Line Items]
Investments in equity securities		97,904	111,297
Unlisted equity [Member]
Accounting Policy [Line Items]
Investments in equity securities		40,543	39,463
Information processing and communications [Member]
Accounting Policy [Line Items]
Depreciation and amortization charges of both owned and capital lease assets		45,818	58,300	56,186
Occupancy and related depreciation [Member]
Accounting Policy [Line Items]
Depreciation and amortization charges of both owned and capital lease assets		¥ 12,106	¥ 13,279	¥ 14,742
Minimum [Member]
Accounting Policy [Line Items]
Ownership percentage		20.00%
Maximum [Member]
Accounting Policy [Line Items]
Ownership percentage		50.00%
Limited partnership [Member] \| Minimum [Member]
Accounting Policy [Line Items]
Ownership percentage		3.00%