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Financial instruments - Notional and Fair Values of TBAs (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
--- | --- | ---
Derivative [Line Items] |  |
Notional, Sale of TBAs | $ 449,065 | $ 574,365
Notional, Purchase of TBAs | 117,573 | 137,572
Fair Value, Sale of TBAs | 3,188 | 5,791
Fair Value, Purchase of TBAs | $ 175 | $ 2,254

X
- Definition Fair value purchases of to be announced securities. + References No definition available. + Details
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Balance Type: | debit
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X
- Definition Fair value sale of to be announced securities. + References No definition available. + Details
Name: | opy_FairValueSaleOfToBeAnnouncedSecurities
Namespace Prefix: | opy_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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X
- Definition Notional amount purchase of to be announced securities. + References No definition available. + Details
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Namespace Prefix: | opy_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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X
- Definition Notional amount sale of to be announced securities. + References No definition available. + Details
Name: | opy_NotionalAmountSaleOfToBeAnnouncedSecurities
Namespace Prefix: | opy_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
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