Discontinued Operations - Assets and Liabilities of Discontinued Operations (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
OMHHF
ASSETS
Securities owned	$ 560,000	$ 3,600,000

Disposal Group, Including Discontinued Operation, Securities Owned

No definition available.

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