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Bank Call Loans - Additional Information (Detail) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Schedule Of Bank Call Loans [Line Items] |  |  |
Broker call rate | 2.00% | 2.00% |
Interest expense on bank call loans | $ 996,200 | $ 1,200,000 | $ 805,200

X
- Definition Broker call rate as of the balance sheet date. + References No definition available. + Details
Name: | opy_BrokerCallRate
Namespace Prefix: | opy_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Interest Expense on Bank Call Loans + References No definition available. + Details
Name: | opy_InterestExpenseOnBankCallLoans
Namespace Prefix: | opy_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | opy_ScheduleOfBankCallLoansLineItems
Namespace Prefix: | opy_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration