Fair Value Measurements (Recorded Amounts of Major Assets Measured at Fair Value on Nonrecurring Basis) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2023	Mar. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	¥ 149,390	¥ 197,041
Certain investment in affiliates	5,003	2,511
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certain investment in affiliates	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certain investment in affiliates	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certain investment in affiliates	5,003	2,511
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	10,542	1,139
Real estate collateral-dependent loans (net of allowance for credit losses)	3,725	5,970
Investment in operating leases, property under facility operations, office facilities and other assets		4,568
Investment in operating leases and property under facility operations	480
Certain equity securities	12,493	11,794
Certain investment in affiliates		4,013
Assets measured at fair value on a nonrecurring basis	27,240	27,484
Fair Value, Measurements, Nonrecurring \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0	0
Real estate collateral-dependent loans (net of allowance for credit losses)	0	0
Investment in operating leases, property under facility operations, office facilities and other assets		0
Investment in operating leases and property under facility operations	0
Certain equity securities	0	0
Certain investment in affiliates		3,587
Assets measured at fair value on a nonrecurring basis	0	3,587
Fair Value, Measurements, Nonrecurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	10,451	1,139
Real estate collateral-dependent loans (net of allowance for credit losses)	0	0
Investment in operating leases, property under facility operations, office facilities and other assets		31
Investment in operating leases and property under facility operations	0
Certain equity securities	12,493	11,794
Certain investment in affiliates		0
Assets measured at fair value on a nonrecurring basis	22,944	12,964
Fair Value, Measurements, Nonrecurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	91	0
Real estate collateral-dependent loans (net of allowance for credit losses)	3,725	5,970
Investment in operating leases, property under facility operations, office facilities and other assets		4,537
Investment in operating leases and property under facility operations	480
Certain equity securities	0	0
Certain investment in affiliates		426
Assets measured at fair value on a nonrecurring basis	¥ 4,296	¥ 10,933

Investment in operating leases and property under facility operations.

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- Definition

Investment in operating leases, property under facility operations, office facilities and other assets.

+ References

No definition available.

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- Definition

Real estate collateral-dependent loans (net allowance probable loan losses).

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482736/825-10-45-1A

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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 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-3

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- Definition

Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

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