Partners Equity of The Operating Partnership (DetailsTextuals) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended				12 Months Ended		0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended				0 Months Ended			12 Months Ended		0 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Aug. 05, 2010	Dec. 31, 2011 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 13, 2011 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Feb. 27, 2004 BRANDYWINE OPERATING PARTNERSHIP, L.P. 7.375% Series E Preferred Shares	Dec. 31, 2011 BRANDYWINE OPERATING PARTNERSHIP, L.P. 7.375% Series E Preferred Shares	Dec. 31, 2010 BRANDYWINE OPERATING PARTNERSHIP, L.P. 7.375% Series E Preferred Shares	Dec. 30, 2003 BRANDYWINE OPERATING PARTNERSHIP, L.P. 7.50% Series D Preferred Shares	Dec. 31, 2011 BRANDYWINE OPERATING PARTNERSHIP, L.P. 7.50% Series D Preferred Shares	Dec. 31, 2010 BRANDYWINE OPERATING PARTNERSHIP, L.P. 7.50% Series D Preferred Shares	Dec. 31, 2011 Class A Units	Dec. 31, 2010 Class A Units	Dec. 23, 2011 Class F (2010) Units	Aug. 05, 2010 Class F (2010) Units BRANDYWINE OPERATING PARTNERSHIP, L.P.	Jan. 19, 2012 Dividend Declared	Dec. 31, 2011 Dividend Declared 7.375% Series E Preferred Shares	Dec. 31, 2011 Dividend Declared 7.50% Series D Preferred Shares	Jan. 17, 2012 Dividend Paid 7.375% Series E Preferred Shares	Jan. 17, 2012 Dividend Paid 7.50% Series D Preferred Shares	Jan. 19, 2012 Dividend Paid BRANDYWINE OPERATING PARTNERSHIP, L.P.
Partners Equity of The Operating Partnership (Textuals) [Abstract]
Preferred units, shares issued							2,300,000	2,300,000	2,300,000	2,000,000	2,000,000	2,000,000
Preferred units, aggregate liquidation preference							$ 57.5			$ 50.0
Preferred units, liquidation preference per unit							$ 25			$ 25
Percentage of Preferential return							7.375%	7.375%	7.375%	7.50%	7.50%	7.50%						7.375%	7.50%
Redeemable limited partnership units potential cash redemption value based on closing market price	$ 9.50	$ 11.65	$ 11.40
Limited partners capital account, units outstanding													2,698,647	2,791,640
Distribution Declared per common partnership unit						$ 0.15											$ 0.15
Distribution Declared for common partnership unitholders																						21.5
Distributions paid Preferred unitholders																				1.1	0.9
Net proceeds contributed by Parent Company	$ 8.0
Issue of shares under Offering Program	679,285
Common partnership units issued to the parent company					679,285										7,111,112
Partnership units issued for acquisition																7,111,112
Redemption price of partnership unit				either for an amount, per unit, of cash equal to the market price of one of the Parent Company’s common share (based on the five-day trading average ending on the date of the exchange) or for one of the Parent Company’s common share
Common Partnership Units Issued	6,421,553
Remaining shares available for sales	8,578,447