Leases - Lessor: Investment in Operating Leases (Detail) - Investment in Operating Leases - JPY (¥) ¥ in Millions	Mar. 31, 2024	Mar. 31, 2023
Property Subject to or Available for Operating Lease [Line Items]
Property Subject to or Available for Operating Lease, Gross	¥ 2,666,119	¥ 2,263,163
Accumulated depreciation	(936,001)	(865,942)
Net	1,730,118	1,397,221
Right-of-use assets	87,359	98,417
Accrued rental receivables	54,230	45,123
Allowance for doubtful receivables on operating leases	(3,133)	(3,583)
Investment in Operating Leases	1,868,574	1,537,178
Transportation equipment
Property Subject to or Available for Operating Lease [Line Items]
Property Subject to or Available for Operating Lease, Gross	1,892,410	1,521,865
Measuring and information-related equipment
Property Subject to or Available for Operating Lease [Line Items]
Property Subject to or Available for Operating Lease, Gross	377,195	342,591
Real estate
Property Subject to or Available for Operating Lease [Line Items]
Property Subject to or Available for Operating Lease, Gross	308,989	319,074
Other
Property Subject to or Available for Operating Lease [Line Items]
Property Subject to or Available for Operating Lease, Gross	¥ 87,525	¥ 79,633

Allowances for doubtful receivables on operating leases.

No definition available.

Name:	ck0001070304_AllowancesForDoubtfulReceivablesOnOperatingLeases
Namespace Prefix:	ck0001070304_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Operating lease right of use asset Net.

+ References

No definition available.

+ Details

Name:	ck0001070304_OperatingLeaseRightOfUseAssetNet
Namespace Prefix:	ck0001070304_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Operating Leases Accrued Rental Receivable

+ References

No definition available.

+ Details

Name:	ck0001070304_OperatingLeasesAccruedRentalReceivable
Namespace Prefix:	ck0001070304_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Property Subject to or Available for Operating Lease, Net of Accumulated Depreciation

+ References

No definition available.

+ Details

Name:	ck0001070304_PropertySubjectToOrAvailableForOperatingLeaseNetOfAccumulatedDepreciation
Namespace Prefix:	ck0001070304_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated depreciation of lessor's underlying asset for which right to use has been conveyed to lessee under operating lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 840
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481501/840-20-50-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479773/842-30-50-13

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-SubTopic 20
-Topic 840
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481532/840-20-45-3

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482099/360-10-50-1

+ Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAccumulatedDepreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before accumulated depreciation, of lessor's underlying asset for which right to use has been conveyed to lessee under operating lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 840
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481501/840-20-50-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479773/842-30-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482099/360-10-50-1

Reference 4: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-SubTopic 20
-Topic 840
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481532/840-20-45-2

+ Details

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

- 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://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 840
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481501/840-20-50-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479773/842-30-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482099/360-10-50-1

+ Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated depreciation, of lessor's underlying asset for which right to use has been conveyed to lessee under operating lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 840
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481501/840-20-50-4

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479773/842-30-50-13

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482099/360-10-50-1

+ Details

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

- Details

Name:	us-gaap_LeaseContractualTermAxis=ck0001070304_OperatingLeaseInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=us-gaap_TransportationEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=ck0001070304_MeasuringAndInformationRelatedEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=ck0001070304_RealEstateAssetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=ck0001070304_OtherLeasedEquipmentAndPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: