Condensed Consolidating Financial Information - Narrative (Details)	6 Months Ended
Jun. 30, 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