Consolidated Balance Sheets (Parentheticals) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Preferred Stock, Shares Authorized	20,000,000us-gaap_PreferredStockSharesAuthorized	20,000,000us-gaap_PreferredStockSharesAuthorized
Preferred Stock, Dividend Rate, Percentage	6.90%	6.90%
Preferred Stock, Shares Issued	4,000,000us-gaap_PreferredStockSharesIssued	4,000,000us-gaap_PreferredStockSharesIssued
Preferred Stock, Shares Outstanding	4,000,000us-gaap_PreferredStockSharesOutstanding	4,000,000us-gaap_PreferredStockSharesOutstanding
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	400,000,000us-gaap_CommonStockSharesAuthorized	400,000,000us-gaap_CommonStockSharesAuthorized
Common Stock, Shares, Issued	179,745,598us-gaap_CommonStockSharesIssued	179,293,160us-gaap_CommonStockSharesIssued
Common Stock, Shares, Outstanding	179,745,598us-gaap_CommonStockSharesOutstanding	179,293,160us-gaap_CommonStockSharesOutstanding
Common shares in grantor trust	694,691bdn_CommonSharesInGrantorTrust	384,536bdn_CommonSharesInGrantorTrust
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Preferred Stock, Dividend Rate, Percentage	6.90%	6.90%
Preferred Stock, Shares Issued	4,000,000	4,000,000
Preferred Stock, Shares Outstanding	4,000,000	4,000,000
Redeemable Limited Partnership Units Issued	1,535,102	1,535,102
Redeemable Limited Partnership Units Outstanding	1,535,102	1,535,102
General Partners' Capital Account, Units Issued	179,745,598	179,293,160
General Partners' Capital Account, Units Outstanding	179,745,598	179,293,160

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