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Segment Information - Reported Revenue and Profit Before Income Taxes (Parenthetical) (Detail) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2012 | Sep. 30, 2011 | Sep. 30, 2012 | Sep. 30, 2011
Asset Management [Member] |  |  |  |
Operating Statistics [Line Items] |  |  |  |
Asset management revenue | 22.50% | 22.50% | 22.50% | 22.50%
Private Client [Member] |  |  |  |
Operating Statistics [Line Items] |  |  |  |
Asset management revenue | 77.50% | 77.50% | 77.50% | 77.50%

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- Definition Asset management revenue. + References No definition available. + Details
Name: | opy_AssetManagementRevenue
Namespace Prefix: | opy_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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