Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Preferred Stock, Value, Issued	96,850
Brandywine Realty Trust's equity:
Preferred shares, shares authorized	20,000,000	20,000,000
Common shares of Brandywine Realty Trust's beneficial interest, par value (in dollars per share)	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	143,438,501	142,690,755
Common shares of Brandywine Realty Trust's beneficial interest, shares outstanding	143,438,501	142,690,755
Common shares in grantor trust	290,745	292,646
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Brandywine Realty Trust's equity:
Preferred shares, dividend rate (as a percent)	6.90%	0.00%
Preferred shares, shares issued	4,000,000	0
Preferred shares, shares outstanding	4,000,000	0
Redeemable Limited Partnership, units issued	2,657,721	2,698,648
Redeemable Limited Partnership, units outstanding	2,657,721	2,698,648
General Partners' Capital account, units issued	143,438,501	142,690,755
General Partners' Capital account, units outstanding	143,438,501	142,690,755
7.50% Series C Preferred Shares
Preferred Stock, Value, Issued	0	20
Brandywine Realty Trust's equity:
Preferred shares, dividend rate (as a percent)	0.00%	7.50%
Preferred shares, par value (in dollars per share)	0	0.01
Preferred shares, shares issued	0	2,000,000
Preferred shares, shares outstanding	0	2,000,000
7.375% Series D Preferred Shares
Preferred Stock, Value, Issued	23	23
Brandywine Realty Trust's equity:
Preferred shares, dividend rate (as a percent)	7.375%	7.375%
Preferred shares, par value (in dollars per share)	0.01	0.01
Preferred shares, shares issued	2,300,000	2,300,000
Preferred shares, shares outstanding	2,300,000	2,300,000
7.50% Series D Preferred Shares | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Preferred Stock, Value, Issued	0	47,912
Brandywine Realty Trust's equity:
Preferred shares, dividend rate (as a percent)		7.50%
Preferred shares, shares issued		2,000,000
Preferred shares, shares outstanding		2,000,000
7.375% Series E Preferred Shares
Preferred Stock, Value, Issued	40	0
Brandywine Realty Trust's equity:
Preferred shares, dividend rate (as a percent)	6.90%
Preferred shares, par value (in dollars per share)	0.01
Preferred shares, shares issued	4,000,000
Preferred shares, shares outstanding	4,000,000
7.375% Series E Preferred Shares | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Preferred Stock, Value, Issued	55,538	55,538
Brandywine Realty Trust's equity:
Preferred shares, dividend rate (as a percent)	7.375%	7.375%
Preferred shares, shares issued	2,300,000	2,300,000
Preferred shares, shares outstanding	2,300,000	2,300,000