Beneficiaries Equity of the Parent Company (Details Textuals) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended			9 Months Ended				0 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	May 15, 2014	May 14, 2014	Sep. 30, 2014 Series E Preferred Stock [Member]	Sep. 30, 2014 Offering Program [Member]	Nov. 05, 2013 Offering Program [Member]	Oct. 06, 2014 Dividend Paid [Member]	Oct. 15, 2014 Dividend Paid [Member] Series E Preferred Stock [Member]	Sep. 30, 2014 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Sep. 30, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Sep. 30, 2014 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Sep. 30, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Oct. 06, 2014 BRANDYWINE OPERATING PARTNERSHIP, L.P. Dividend Paid [Member]
Class of Stock [Line Items]
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	$ 0.04	$ 0.06	$ 0.01	$ 0.08									$ 0.04	$ 0.06	$ 0.01	$ 0.08
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	$ 0.04	$ 0.06	$ 0.01	$ 0.08									$ 0.04	$ 0.06	$ 0.01	$ 0.08
Discontinued Operations attributable to common shareholders/unitholders, Basic	$ 0.00	$ 0.00	$ 0.01	$ 0.03									$ 0.00	$ 0.00	$ 0.01	$ 0.03
Stock Issued During Period, Shares, New Issues			21,850,000
Proceeds from Issuance of Common Stock			$ 335,016	$ 181,527											$ 335,016	$ 181,527
Distributions payable	28,857		28,857		25,584						27,200		28,857		28,857		25,584	27,200
Preferred Stock, Shares Issued	4,000,000		4,000,000		4,000,000								4,000,000		4,000,000		4,000,000
Preferred Stock, Dividend Rate, Percentage			6.90%		6.90%			6.90%							6.90%		6.90%
Preferred Stock, Liquidation Preference Per Share								$ 25.00
Dividends, Preferred Stock, Cash			$ 5,175	$ 5,175								$ 1,700
Shares of Beneficial Interest, Shares Authorized						420,000,000	220,000,000
Shares Authorized For Equity Offering Program										16,000,000
Remaining Shares Available For Sales									16,000,000
Common Stock, Shares Authorized	400,000,000		400,000,000		200,000,000	400,000,000	200,000,000
Preferred Stock, Shares Authorized	20,000,000		20,000,000		20,000,000	20,000,000
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	539,200		539,200
Discontinued Operations attributable to common shareholders/unitholders, Diluted	$ 0.00	$ 0.00	$ 0.01	$ 0.03									$ 0.00	$ 0.00	$ 0.01	$ 0.03
Net income (loss) attributable to common shareholders/unitholders, Basic	$ 0.04	$ 0.06	$ 0.02	$ 0.11									$ 0.04	$ 0.06	$ 0.02	$ 0.11
Net income attributable to common shareholders/unitholders, Diluted	$ 0.04	$ 0.06	$ 0.02	$ 0.11									$ 0.04	$ 0.06	$ 0.02	$ 0.11