Supplemental Guarantor Condensed Consolidated Financial Statements - Additional Information (Narrative) (Details)	3 Months Ended
Mar. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Interest owned by the holding company	100.00%

The percentage of ownership the holding company owns the guarantors.

No definition available.

Name:	opy_InterestOwnershipByHoldingCompany
Namespace Prefix:	opy_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration