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Deferred Costs Deferred Costs (Details Textuals) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2013 | Mar. 31, 2012
Deferred Costs (Textuals) [Abstract] |  |
Capitalized Internal Direct Leasing Costs | $ 1.5 | $ 1.3

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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