Beneficiaries Equity of the Parent Company Beneficiaries Equity of the Parent Company (Details Textuals) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended			3 Months Ended	12 Months Ended	0 Months Ended	3 Months Ended			3 Months Ended	12 Months Ended		36 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Class A Units [Member]	Dec. 31, 2012 Class A Units [Member]	Apr. 15, 2013 Series E Preferred Stock [Member]	Mar. 31, 2013 Series E Preferred Stock [Member]	Mar. 13, 2013 Dividend Declared [Member]	Mar. 13, 2013 Dividend Paid [Member]	Mar. 31, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2012 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Mar. 13, 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				1,845,737	2,657,721
Preferred Stock, Shares Issued										4,000,000	4,000,000
Preferred Stock, Dividend Rate, Percentage							6.90%			6.90%	6.90%
Preferred Stock, Liquidation Preference Per Share							$ 25.00
Dividends, Preferred Stock, Cash	$ (1,725)	$ (1,998)				$ 1,700
Shares Authorized For Equity Offering Program													15,000,000
Distribution Declared Per Common Partnership Unit								$ 0.15				$ 0.15
Distributions payable	$ 23,684		$ 23,652						$ 21,700	$ 23,684	$ 23,652	$ 21,700
Maximum percentage of Gross sale price per share compensation to sales agents													2.00%
Number Of Shares Sold By Company													6,421,553
Average Sales Price Per Share													$ 12.50
Additional shares Expected to be purchased under program	500,000