Consolidated Balance Sheets Consolidated Balance Sheets (Parentheticals) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	143,712,578	143,538,733
Common Stock, Shares, Outstanding	143,712,578	143,538,733
Common shares in grantor trust	315,753	290,745
Series E Preferred Stock [Member]
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
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
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	1,845,737	1,845,737
Redeemable Limited Partnership Units Outstanding	1,845,737	1,845,737
General Partners' Capital Account, Units Issued	143,712,578	143,538,733
General Partners' Capital Account, Units Outstanding	143,712,578	143,538,733