Beneficiaries Equity of the Parent Company Beneficiaries Equity of the Parent Company (Details Textuals) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	9 Months Ended		12 Months Ended	9 Months Ended	12 Months Ended	0 Months Ended	9 Months Ended	36 Months Ended	9 Months Ended		9 Months Ended		12 Months Ended		36 Months Ended
	Apr. 10, 2013	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Class A Units [Member]	Dec. 31, 2012 Class A Units [Member]	Jul. 15, 2013 Series E Preferred Stock [Member]	Sep. 30, 2013 Series E Preferred Stock [Member]	Mar. 10, 2013 Offering Program [Member]	Sep. 30, 2013 Dividend Declared [Member]	Oct. 18, 2013 Dividend Paid [Member]	Sep. 30, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Sep. 30, 2012 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2012 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Oct. 18, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Mar. 10, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P. Offering Program [Member]
Class of Stock [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount					1,763,739	2,657,721
Stock Issued During Period, Shares, New Issues	12,650,000
Additional shares granted under option to purchase in public offering	1,650,000
Proceeds from Issuance of Common Stock	$ 181,700	$ 181,527	$ 0									$ 181,527	$ 0
Common Stock, Dividends, Per Share, Declared										$ 0.15
Distributions payable		25,579		23,652							23,800	25,579		23,652	23,800
Preferred Stock, Shares Issued		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	$ 7,832				$ 1,700
Common Stock, Shares Authorized		200,000,000		200,000,000					15,000,000
Maximum percentage of Gross sale price per share compensation to sales agents									2.00%
Stock Issued During Period, Shares, Other									6,421,553							6,421,553
Average Sales Price Per Share									$ 12.50
Additional shares Expected to be purchased under program		539,200