Net Amounts of Assets Presented on the Balance Sheet

(68,055)

(3,028)

5,842

Cash Collateral Received

Gross Amounts of Recognized Assets

5,842

Securities borrowed

137,177

158,612

Net Amounts of Assets Presented on the Balance Sheet

137,177

158,612

(130,568)

(149,946)

Cash Collateral Received

Gross Amounts of Recognized Assets

6,609

8,666

Total

205,232

167,482

Net Amounts of Assets Presented on the Balance Sheet

(68,055)

(3,028)

137,177

164,454

(130,568)

(149,946)

Cash Collateral Received

6,609

14,508

Repurchase agreements

U.S. Treasury securities

643,410

Net Amounts of Liabilities Presented on the Balance Sheet

(68,055)

(3,028)

931,754

640,382

(931,754)

(632,521)

Cash Collateral Pledged

7,861

Securities loaned

Equity securities

284,987

Net Amounts of Liabilities Presented on the Balance Sheet

235,498

284,987

(229,156)

(276,688)

Cash Collateral Pledged

Gross Amounts of Recognized Liabilities

6,342

8,299

Total

1,235,307

928,397

Net Amounts of Liabilities Presented on the Balance Sheet

(68,055)

(3,028)

1,167,252

925,369

(1,160,910)

(909,209)

Cash Collateral Pledged

$ 6,342

$ 16,160

Derivative Asset, Securities Purchased under Agreement to Resell, Securities Borrowed, Not Offset Against Collateral

No definition available.

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

Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Amount Not Offset Against Collateral

No definition available.

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

Securities Borrowed, Amount Not Offset Against Collateral

No definition available.

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

Securities Loaned, Amount Not Offset Against Collateral

No definition available.

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

Securities Purchased Under Agreement To Resell, Amount Not Offset Against Collateral

No definition available.

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

Securities Sold Under Agreements To Repurchase, Amount Not Offset Against Collateral

No definition available.

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

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets, securities purchased under agreements to resell and securities borrowed.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 13
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-13

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-22

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-20

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-21

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

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

Amount of obligation to return securities collateral under master netting arrangements that have not been offset against derivative assets, securities purchased under agreements to resell and securities borrowed.

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

Amount, before effects of master netting arrangements, of derivative assets, securities purchased under agreements to resell and securities borrowed. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-7

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

Amount of liability associated with derivative assets, securities purchased under agreements to resell and securities borrowed.

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

Amount, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of derivative assets, securities purchased under agreements to resell and securities borrowed, offset against an obligation to return collateral under a master netting arrangement.

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

Amount of asset associated with derivative liabilities, securities sold under agreements to repurchase and securities loaned.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-8

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-20

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-21

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

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities, securities sold under agreements to repurchase and securities loaned.

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

Amount of right to receive securities collateral under master netting arrangements that have not been offset against derivative liabilities, securities sold under agreements to repurchase and securities loaned.

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

Amount, before effects of master netting arrangements, of derivative liabilities, securities sold under agreements to repurchase and securities loaned. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-7

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

Amount, after effects of master netting arrangements, deduction of liabilities not subject to a master netting arrangement and elected not to be offset, of derivative liabilities, securities sold under agreements to repurchase and securities loaned, offset against a right to receive collateral.

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

No definition available.

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

No definition available.

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

No definition available.

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

No definition available.

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

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against securities borrowed.

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

Amount of obligation to return securities collateral under master netting arrangements that have not been offset against securities borrowed.

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

Amount, before effects of master netting arrangements, of securities borrowed from entities in exchange for collateral. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-7

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

Amount of liability associated with securities borrowed from entities in exchange for collateral.

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

Amount, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of securities borrowed from entities in exchange for collateral, offset against an obligation to return collateral under a master netting arrangement.

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

No definition available.

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

Amount of asset associated with securities loaned to entities in exchange for collateral.

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

Amount of right to receive cash collateral under master netting arrangements that have not been offset against securities loaned.

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

Amount of right to receive securities collateral under master netting arrangements that have not been offset against securities loaned.

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

Amount, before effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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

Amount, after effects of master netting arrangements, deduction of liabilities not subject to a master netting arrangement and elected not to be offset, of securities loaned to entities in exchange for collateral, offset against a right to receive collateral.

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

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against securities purchased under agreement to resell.

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

Amount of obligation to return securities collateral under master netting arrangements that have not been offset against securities purchased under agreement to resell.

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

Amount, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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

Amount of liability associated with funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-8

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-20

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

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

Amount, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price, offset against an obligation to return collateral.

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

No definition available.

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

Amount of asset associated with funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-8

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-20

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

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

Amount of right to receive cash collateral under master netting arrangements that have not been offset against securities sold under agreement to repurchase.

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

Amount of right to receive securities collateral under master netting arrangements that have not been offset against securities sold under agreement to repurchase.

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

Amount, before effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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

Amount, after effects of master netting arrangements, deduction of liabilities not subject to a master netting arrangement and elected not to be offset, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price, offset against a right to receive collateral.