Credit concentration receivable from major broker dealers.

No definition available.

Name:	opy_CreditConcentrationReceivableFromMajorBrokerDealers
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Margin deposited with option clearing corporation.

+ References

No definition available.

+ Details

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

- Definition

Distribution on securities received by trust.

+ References

No definition available.

+ Details

Name:	opy_DistributionOnSecuritiesReceivedByTrust
Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value of loans collateralized by customer securities.

+ References

No definition available.

+ Details

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Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of loans collateralized by firm.

+ References

No definition available.

+ Details

Name:	opy_FairValueOfLoansCollateralizedByFirm
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Balance Type:	debit
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- Definition

Fair value of securities reverse repurchase agreement.

+ References

No definition available.

+ Details

Name:	opy_FairValueOfSecuritiesReverseRepurchaseAgreement
Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Investments held in trust fair value.

+ References

No definition available.

+ Details

Name:	opy_InvestmentsHeldInTrustFairValue
Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Mortgage loan guarantee period.

+ References

No definition available.

+ Details

Name:	opy_MortgageLoanGuaranteePeriod
Namespace Prefix:	opy_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Pledged securities owned and pledged as collateral amount eligible to be repledged by counterparty carrying value.

+ References

No definition available.

+ Details

Name:	opy_PledgedSecuritiesOwnedAndPledgedAsCollateralAmountEligibleToBeRepledgedByCounterpartyCarryingValue
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Receivables from Brokers-Dealers and Clearing Organizations, Number of Major Broker-Dealers

+ References

No definition available.

+ Details

Name:	opy_ReceivablesfromBrokersDealersandClearingOrganizationsNumberofMajorBrokerDealers
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Securities owned and pledged as collateral amount not eligible to be repledged by counterparty carrying value.

+ References

No definition available.

+ Details

Name:	opy_SecuritiesOwnedAndPledgedAsCollateralAmountNotEligibleToBeRepledgedByCounterpartyCarryingValue
Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amounts due on short-term bank loans secured by customers' securities on the balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it is permitted by contract or custom to sell or re-pledge to counterparties as collateral.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

+ Details

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

- Definition

Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it has sold or re-pledged to counterparties as collateral.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

+ Details

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

- Details

Name:	us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

- Definition

The carrying amount of the outstanding balance due under the mortgage loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

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

- Definition

The carrying amount (fair value) as of the balance sheet date of securities held that had been pledged by counterparties under financing and lending arrangements, pursuant to which the entity has the right by agreement or custom to sell or re-pledge such securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5086-111524

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

- Details

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- Details

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- Details

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- Details

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Collateralized Transactions - Narrative (Details) (USD $)	0 Months Ended	3 Months Ended
	Sep. 26, 2013	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Bank call loans		$ 101,400,000us-gaap_BankLoans		$ 59,400,000us-gaap_BankLoans
Customer securities under customer margin loans available to be pledged		1,300,000,000
Customer securities under customer margin loans agreement available to be repledged		133,100,000
Customer securities deposited to secure obligations and margin requirements under option contracts		386,400,000
Outstanding letters of credit		0
Fair value of the reverse repurchase agreements				250,000,000
Carrying value of pledged securities owned that can be sold or re-pledged by the counterparty		501,600,000		518,100,000
Carrying value of securities owned by the Company loaned or pledged		196,800,000		149,100,000
Amount of first interim distribution	9,500,000
Fair value of the company's investment on reserves not paid in first distribution			600,000opy_InvestmentsHeldInTrustFairValue
Receivable from brokers and clearing organizations, number of major broker-dealers		2
Receivable from brokers and clearing organizations		113,000,000
Credit Concentration Risk [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guaranteed mortgages for a period		15 days
Variable interest rate under warehouse facility		1 month LIBOR
Interest expense		125,000	144,000
Warehouse Facility [Member] \| Credit Concentration Risk [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Outstanding under the warehouse facility line		87,600,000
Reverse Repurchase Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer securities under customer margin loans agreement available to be repledged		222,300,000		314,100,000
Securities received as collateral under securities borrowed transaction with market value		222,300,000		312,600,000
Securities Borrowed Transactions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Customer securities under customer margin loans agreement available to be repledged		24,400,000		4,400,000
Securities received as collateral under securities borrowed transaction with market value		258,400,000		235,100,000
Corporate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Collateralized loans, collateralized by firm		196,600,000
Other Than Corporate Customer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Collateralized loans, collateralized by customer securities		$ 209,200,000