Debt instrument premature redemption period.

No definition available.

Name:	ck0001070304_DebtInstrumentPrematureRedemptionPeriod
Namespace Prefix:	ck0001070304_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instruments maturity year.

+ References

No definition available.

+ Details

Name:	ck0001070304_DebtInstrumentsMaturityYear
Namespace Prefix:	ck0001070304_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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.

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+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ References

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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+ Details

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

- Definition

The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount of collateralized debt obligations with maturities initially due after one year or beyond the operating cycle, if longer, excluding the current portion. Obligations include, but not limited to, mortgage loans, chattel loans, and other borrowings secured by assets.

+ References

+ Details

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

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_PledgingPurposeAxis=ck0001070304_SecuredInvestmentsMember
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_PledgingPurposeAxis=ck0001070304_LoansAndLeasesReceivableCollateralForSecuredBorrowingsMember
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Period Type:

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Period Type:

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Period Type:

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Period Type:

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Balance Type:
Period Type:

- Details

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Period Type:

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Period Type:

Short-Term and Long-Term Debt - Additional Information (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Borrowings	¥ 5,733,118	¥ 5,626,376
Net amortization expenses of bond premiums and discounts, deferred issuance costs of bonds and medium-term notes	1,455	1,247	¥ 1,093
Total committed credit lines	795,634	758,667
Available credit lines	598,079	559,322
Long-term committed credit lines	502,177	¥ 495,474
Secured by shares of subsidiaries [Member]
Debt Instrument [Line Items]
Secured debt	89,021
Secured by investment in affiliates [Member]
Debt Instrument [Line Items]
Secured debt	180,248
Secured by loans to subsidiaries [Member]
Debt Instrument [Line Items]
Secured debt	154,926
Investment in securities for collateral deposits and deposits for real estate transaction [Member]
Debt Instrument [Line Items]
Secured debt	14,708
Subordinated Syndicated Loan
Debt Instrument [Line Items]
Borrowings	44,000
Subordinated Syndicated Loan \| Loan Maturing in 5 Year
Debt Instrument [Line Items]
Borrowings			¥ 34,000	¥ 10,000
Maturity year of loan			2083	2082
Unsecured subordinated bonds premature redemption period			5 years	5 years
Unsecured Subordinated Debt
Debt Instrument [Line Items]
Borrowings	150,000
Unsecured subordinated bonds face value						¥ 40,000
Unsecured subordinated bonds year of maturity						2080
Unsecured Subordinated Debt One
Debt Instrument [Line Items]
Unsecured subordinated bonds face value	¥ 60,000				¥ 50,000
Unsecured subordinated bonds year of maturity	2060				2081
Unsecured Subordinated Debt One \| Premature Redemption Period 5 Years
Debt Instrument [Line Items]
Unsecured subordinated bonds face value					¥ 29,000
Unsecured Subordinated Debt One \| Premature Redemption Period 10 Years
Debt Instrument [Line Items]
Unsecured subordinated bonds face value					¥ 21,000