Partners Equity of the Operating Partnership (Details Textuals) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended		12 Months Ended	9 Months Ended		12 Months Ended	9 Months Ended					0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Sep. 30, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2013 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Sep. 30, 2014 Class A Units [Member]	Sep. 30, 2013 Class A Units [Member]	Sep. 30, 2014 6.90% Series E-linked Preferred Units [Member] BRANDYWINE OPERATING PARTNERSHIP, L.P.	Oct. 06, 2014 Dividend Paid [Member]	Oct. 06, 2014 Dividend Paid [Member] BRANDYWINE OPERATING PARTNERSHIP, L.P.	Oct. 15, 2014 Dividend Paid [Member] 6.90% Series E-linked Preferred Units [Member] BRANDYWINE OPERATING PARTNERSHIP, L.P.	Sep. 10, 2014 Dividend Declared [Member]	Sep. 10, 2014 Dividend Declared [Member] BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount							1,721,905	1,763,739
Dividends Payable, Amount Per Share													$ 0.15	$ 0.15
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		25,584	28,857		25,584				27,200	27,200
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