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Deferred Costs (Details Textuals) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Deferred Costs (Textuals) [Abstract] |  |  |
Capitalized internal direct leasing costs | $ 6.6 | $ 6.2 | $ 5.3

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- Definition Capitalized internal direct leasing costs. + References No definition available. + Details
Name: | bdn_CapitalizedInternalDirectLeasingCosts
Namespace Prefix: | bdn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | bdn_DeferredCostsTextualsAbstract
Namespace Prefix: | bdn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration