Income Taxes (Summary of Amounts of Taxes Paid (Net of Amounts Received)) (Detail) ¥ in Millions	12 Months Ended
Mar. 31, 2026 JPY (¥)
Income Tax Paid, by Individual Jurisdiction [Line Items]
Japan national tax	¥ 52,638
Japan local tax	17,458
Foreign	44,651
Total	114,747
INDIA
Income Tax Paid, by Individual Jurisdiction [Line Items]
Foreign	11,286
Tokyo Metropolitan Government [Member]
Income Tax Paid, by Individual Jurisdiction [Line Items]
Japan local tax	8,437
Other [Member]
Income Tax Paid, by Individual Jurisdiction [Line Items]
Japan local tax	9,021
The Americas
Income Tax Paid, by Individual Jurisdiction [Line Items]
Foreign	10,216
Other [Member]
Income Tax Paid, by Individual Jurisdiction [Line Items]
Foreign	¥ 23,149

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.

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

- Definition

Amount, after income tax refund received, of cash paid to federal (national) tax jurisdiction for tax on income.

+ References

+ Details

Name:	us-gaap_IncomeTaxPaidFederalAfterRefundReceived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, after income tax refund received, of cash paid to foreign tax jurisdiction for tax on income.

+ References

+ Details

Name:	us-gaap_IncomeTaxPaidForeignAfterRefundReceived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, after income tax refund received, of cash paid to state and local tax jurisdictions for tax on income.

+ References

+ Details

Name:	us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, after refund, of cash paid to foreign, federal, state, and local jurisdictions as income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-2A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 23
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-23

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-22

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-2

+ Details

Name:	us-gaap_IncomeTaxesPaidNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	srt_StatementGeographicalAxis=country_IN
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalTaxJurisdictionOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=srt_AmericasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=ck0001070304_OtherCountriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: