Beneficiaries Equity of the Parent Company (Textuals) (Details) - USD ($)				12 Months Ended
	Dec. 08, 2015	Aug. 01, 2014	Apr. 10, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 22, 2015	Nov. 05, 2013
Class of Stock [Line Items]
Distributions payable				$ 28,249,000	$ 28,871,000
Preferred Stock, Dividend Rate, Percentage				6.90%	6.90%
Dividends, Preferred Stock				$ 6,900,000	$ 6,900,000	$ 6,900,000
Issuance of Common Shares of Beneficial Interest, Shares		21,850,000	12,650,000
Net proceeds from issuance of common shares\units				$ 0	$ 335,016,000	181,527,000
Shares Authorized For Equity Offering Program								16,000,000
Additional Shares Granted under Option to Purchase in Public Offering			1,650,000
Authorized Amount							$ 100,000,000
Number of Shares Authorized to be Repurchased							539,200
Repurchased and Retired, Shares				5,209,437
Share Price				$ 12.90
Repurchased and Retired, Value				$ 67,325,000
Common stock price per share				$ 0.01	$ 0.01
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Distributions payable				$ 28,249,000	$ 28,871,000
Preferred Stock, Dividend Rate, Percentage				6.90%	6.90%
Dividends, Preferred Stock				$ 6,900,000	$ 6,900,000	6,900,000
Net proceeds from issuance of common shares\units				$ 0	$ 335,016,000	$ 181,527,000
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage				6.90%
Preferred Stock, Liquidation Preference Per Share				$ 25.00
Offering Program [Member]
Class of Stock [Line Items]
Remaining Shares Available For Sales				16,000,000
Offering Program [Member] | Maximum [Member]
Class of Stock [Line Items]
Fees and Commissions Percentage				2.00%
Dividend Declared [Member]
Class of Stock [Line Items]
Dividends Payable, Amount Per Share	$ 0.15
Dividend Declared [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends Payable, Amount Per Share	$ 0.15
Dividend Paid [Member]
Class of Stock [Line Items]
Distributions payable				$ 26,500,000
Dividend Paid [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Distributions payable				$ 26,500,000
Dividend Paid [Member] | Series E Preferred Stock [Member]
Class of Stock [Line Items]
Dividends, Preferred Stock	$ 1,700,000
Redeemable Common Limited Partnership Units
Class of Stock [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share				1,535,102	1,535,102	1,763,739