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Summary of Significant Accounting Policies Finite-lived intangible assets (Details) | Dec. 31, 2014 Y
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Finite-Lived Intangible Assets [Line Items] |
Finite-Lived Intangible Assets, Net | 7 bdn_MinimumRemainingLeasePeriod
Maximum remaining lease period | 75 bdn_MaximumRemainingLeasePeriod

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- Definition Maximum remaining lease period. + References No definition available. + Details
Name: | bdn_MaximumRemainingLeasePeriod
Namespace Prefix: | bdn_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Minimum remaining lease period. + References No definition available. + Details
Name: | bdn_MinimumRemainingLeasePeriod
Namespace Prefix: | bdn_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration