Consolidated Balance Sheets (Parentheticals) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Preferred Stock, Shares Authorized	20,000,000	20,000,000
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
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	156,916,901	156,731,993
Common Stock, Shares, Outstanding	156,916,901	156,731,993
Common shares in grantor trust	384,571	312,279
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	1,763,739	1,763,739
Redeemable Limited Partnership Units Outstanding	1,763,739	1,763,739
General Partners' Capital Account, Units Issued	156,916,901	156,731,993
General Partners' Capital Account, Units Outstanding	156,916,901	156,731,993