Consolidated Balance Sheets (Parenthetical) (USD $)					12 Months Ended				0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2010 BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2011 7.50% Series C Preferred Shares	Dec. 31, 2010 7.50% Series C Preferred Shares	Dec. 31, 2011 7.375% Series D Preferred Shares	Dec. 31, 2010 7.375% Series D Preferred Shares	Dec. 30, 2003 7.50% Series D Preferred Shares BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2011 7.50% Series D Preferred Shares BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2010 7.50% Series D Preferred Shares BRANDYWINE OPERATING PARTNERSHIP, L.P.	Feb. 27, 2004 7.375% Series E Preferred Shares BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2011 7.375% Series E Preferred Shares BRANDYWINE OPERATING PARTNERSHIP, L.P.	Dec. 31, 2010 7.375% Series E Preferred Shares BRANDYWINE OPERATING PARTNERSHIP, L.P.
Brandywine Realty Trust's equity:
Preferred shares, dividend rate					7.50%	7.50%	7.375%	7.375%	7.50%	7.50%	7.50%	7.375%	7.375%	7.375%
Preferred shares, par value					$ 0.01	$ 0.01	$ 0.01	$ 0.01
Preferred shares, shares authorized	20,000,000	20,000,000
Preferred shares, shares issued					2,000,000	2,000,000	2,300,000	2,300,000	2,000,000	2,000,000	2,000,000	2,300,000	2,300,000	2,300,000
Preferred shares, shares outstanding					2,000,000	2,000,000	2,300,000	2,300,000		2,000,000	2,000,000		2,300,000	2,300,000
Common shares of Brandywine Realty Trust's beneficial interest, par value	$ 0.01	$ 0.01
Common shares of Brandywine Realty Trust's beneficial interest, shares authorized	200,000,000	200,000,000
Common shares of Brandywine Realty Trust's beneficial interest, shares issued	142,690,755	134,601,796
Common shares of Brandywine Realty Trust's beneficial interest, shares outstanding	142,690,755	134,485,117
Common shares in treasury, at cost, shares	0	116,679
Common shares in grantor trust, shares	292,646	291,281
Redeemable Limited Partnership, units issued			2,698,648	9,902,752
Redeemable Limited Partnership, units outstanding			2,698,648	9,902,752
General Partners' Capital account, units issued			142,690,755	134,601,796
General Partners' Capital account, units outstanding			142,690,755	134,485,117