The total amount of ARS the firm purchased and hold.

No definition available.

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Namespace Prefix:	opy_
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- Definition

The amount of ARS the firm committed to purchase from clients.

+ References

No definition available.

+ Details

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

- Definition

Capital commitments relating to investments.

+ References

No definition available.

+ Details

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

- Definition

Eligible investor subject to future buyback potential additional losses related to valuation adjustments.

+ References

No definition available.

+ Details

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Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
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- Definition

Eligible investor subject to future buyback principal value.

+ References

No definition available.

+ Details

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Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Operating lease expiration year.

+ References

No definition available.

+ Details

Name:	opy_OperatingLeaseExpirationYear
Namespace Prefix:	opy_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of auction rates security to be purchased from rendering of award.

+ References

No definition available.

+ Details

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

- Definition

Purchase Commitments Outstanding, Auction Rate Securities Related to Settlements with Regulators

+ References

No definition available.

+ Details

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Namespace Prefix:	opy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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

- Definition

Amount of judgment or settlement awarded to (against) the entity in respect of litigation.

+ References

No definition available.

+ Details

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

- Definition

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

The estimated maximum amount of possible loss from the contingency.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

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

- Definition

The estimated minimum amount of possible loss from the contingency.

+ References

+ Details

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

- Definition

The amount of cash paid for the settlement of litigation or for other legal issues during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

+ Details

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

- Details

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- Details

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Commitments and Contingencies - Additional Information (Narrative) (Details) (USD $)	12 Months Ended			0 Months Ended			6 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 27, 2017	Feb. 27, 2015	Jan. 27, 2015	Jun. 30, 2014	Feb. 09, 2015
Loss Contingencies [Line Items]
Operating leases expiring at various dates through	2028
Rent expense	$ 45,600,000us-gaap_LeaseAndRentalExpense	$ 46,400,000us-gaap_LeaseAndRentalExpense	$ 51,200,000us-gaap_LeaseAndRentalExpense
Capital Commitments Relating To Investments	5,100,000
Minimum estimated range of aggregate loss for legal proceedings	0
Maximum estimated range of aggregate loss for legal proceedings	31,000,000
Purchase Commitments Outstanding, Auction Rate Securities Related to Settlements with Regulators	825,000
Eligible investor subject to future buyback principal value	101,400,000
Eligible investor subject to future buyback potential additional losses related to valuation adjustments	0
Period of auction rates security to be purchased from rendering of the award	30 days
Auction rate securities
Loss Contingencies [Line Items]
Total amount of ARS the firm purchased and hold	98,600,000
Amount of ARS committed to purchase from clients	12,200,000
SEC \| Subsequent Events \| Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Litigation Settlement, Amount						10,000,000
Payments for Legal Settlements				5,000,000	5,000,000
SEC \| Subsequent Events \| Unfavorable Regulatory Action, Disgorgement
Loss Contingencies [Line Items]
Litigation Settlement, Amount						4,200,000
SEC \| Subsequent Events \| Unfavorable Regulatory Action, Prejudgment Interest
Loss Contingencies [Line Items]
Litigation Settlement, Amount						753,500
SEC \| Subsequent Events \| Unfavorable Regulatory Action, Civil Penalties
Loss Contingencies [Line Items]
Litigation Settlement, Amount						5,100,000
United States Department of the Treasury \| Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Litigation Settlement, Expense							20,000,000
United States Department of the Treasury \| Subsequent Events \| Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Litigation Settlement, Amount						10,000,000
Payments for Legal Settlements					$ 5,000,000			$ 5,000,000