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Operating Leases - Additional Information (Details) | 12 Months Ended
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Dec. 31, 2018
Leases Operating [Abstract] |
Lessor, operating lease, description | The Company leases properties to tenants under operating leases with various expiration dates extending to 2082.
Operating lease extending expiration date | 2082

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- Definition Lessor operating lease maximum extending expiration date. + References No definition available. + Details
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Namespace Prefix: | bdn_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_LeasesOperatingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Description of terms and conditions of option to extend lessor's operating lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888428&loc=SL77919359-209981 + Details
Name: | us-gaap_LessorOperatingLeaseOptionToExtend
Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration