Credit Quality of Financial Assets and the Allowance for Credit Losses - Summary of Financial Effect of Modifications of Financing Receivable (Detail) - JPY (¥) ¥ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2023	Sep. 30, 2023
Interest rate reduction \| Consumer borrowers \| Real estate loans
Financing Receivable, Modifications [Line Items]
Interest rate reduction, Minimum limit		3.90%
Interest rate reduction, Maximum limit		0.00%
Interest rate reduction \| Consumer borrowers \| Card loans
Financing Receivable, Modifications [Line Items]
Interest rate reduction, Minimum limit	12.70%	12.60%
Interest rate reduction, Maximum limit	0.40%	0.40%
Interest rate reduction \| Consumer borrowers \| Other
Financing Receivable, Modifications [Line Items]
Interest rate reduction, Minimum limit	12.40%	14.20%
Interest rate reduction, Maximum limit	1.80%	2.50%
Term extension \| Consumer borrowers \| Real estate loans
Financing Receivable, Modifications [Line Items]
Term extension	1 year	1 year
Term extension \| Consumer borrowers \| Card loans
Financing Receivable, Modifications [Line Items]
Term extension	6 years 7 months 6 days	6 years 7 months 6 days
Term extension \| Consumer borrowers \| Other
Financing Receivable, Modifications [Line Items]
Term extension	4 years 10 months 24 days	4 years 9 months 18 days
Term extension \| Corporate borrowers \| Real estate companies in Japan \| Japan
Financing Receivable, Modifications [Line Items]
Term extension		6 months
Term extension \| Corporate borrowers \| Commercial, industrial and other companies in Japan \| Japan
Financing Receivable, Modifications [Line Items]
Term extension	6 months	7 months 6 days
Term extension \| Corporate borrowers \| Commercial, industrial and other companies in overseas \| Overseas
Financing Receivable, Modifications [Line Items]
Term extension	4 years 8 months 12 days	4 years 8 months 12 days
Principal forgiveness \| Consumer borrowers \| Real estate loans
Financing Receivable, Modifications [Line Items]
Principal forgiveness	¥ 0	¥ 1
Principal forgiveness \| Consumer borrowers \| Card loans
Financing Receivable, Modifications [Line Items]
Principal forgiveness	40	92
Principal forgiveness \| Consumer borrowers \| Other
Financing Receivable, Modifications [Line Items]
Principal forgiveness	177	336
Principal forgiveness \| Corporate borrowers \| Commercial, industrial and other companies in overseas \| Overseas
Financing Receivable, Modifications [Line Items]
Principal forgiveness	3	108
Principal forgiveness \| Net investment in leases \| Overseas
Financing Receivable, Modifications [Line Items]
Principal forgiveness	¥ 0	¥ 0

Financing receivable weighted average contractual interest rate before modification.

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- Definition

Financing receivable weighted average contractual interest rate before modification.

+ References

No definition available.

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- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481962/310-10-50-34

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- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

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- Definition

Amount of increase (decrease) in amortized cost of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
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-Section 55
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
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-Paragraph 33
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-33

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