Beneficiaries Equity of The Parent Company (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Numerator
Income (loss) from continuing operations, Basic									$ (30,154)	$ (18,965)	$ (37,325)
Income (loss) from continuing operations, Diluted									(30,154)	(18,965)	(37,325)
Net income (loss) from continuing operations attributable to non-controlling interests, Basic									736	769	946
Net income (loss) from continuing operations attributable to non-controlling interests, Diluted									736	769	946
Amount allocated to unvested restricted shareholders/unitholders, Basic									(376)	(505)	(512)
Amount allocable to unvested restricted shareholders, Diluted									(376)	(505)	(512)
Preferred share/unit dividends, Basic									(10,405)	(7,992)	(7,992)
Preferred share/unit dividends, Diluted									(10,405)	(7,992)	(7,992)
Redemption Premium, Basic									(4,052)	0	0
Redemption Premium, Diluted									(4,052)	0	0
Income (loss) from continuing operations available to common shareholders/unitholders, Basic									(44,251)	(26,693)	(44,883)
Income (loss) from continuing operations available to common shareholders/unitholders, Diluted									(44,251)	(26,693)	(44,883)
Income from discontinued operations									36,683	14,250	19,719
Income (loss) from discontinued operations, Diluted									36,683	14,250	19,719
Discontinued operations attributable to non-controlling interests - LP units									(670)	(553)	(414)
Discontinued operations attributable to non-controlling interests, diluted									(670)	(553)	(414)
Discontinued operations attributable to common shareholders, Basic									36,013	13,697	19,305
Discontinued operations attributable to common shareholders, Diluted									36,013	13,697	19,305
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust									(8,238)	(12,996)	(25,578)
Net income (loss) available to common shareholders/unitholders, Diluted									$ (8,238)	$ (12,996)	$ (25,578)
Denominator
Weighted-average units outstanding, Basic									143,257,097	135,444,424	131,743,275
Weighted-average shares/units outstanding, Diluted									143,257,097	135,444,424	131,743,275
Earnings per Common Share:
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Basic									$ (0.31)	$ (0.20)	$ (0.34)
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Diluted									$ (0.31)	$ (0.20)	$ (0.34)
Discontinued operations attributable to common shareholders/unitholders, Basic									$ 0.25	$ 0.10	$ 0.15
Discontinued operations attributable to common shareholders, Diluted									$ 0.25	$ 0.10	$ 0.15
Net income (loss) attributable to common shareholders/unitholders, Basic	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ (0.05)	$ 0.03	$ (0.06)	$ (0.02)	$ (0.06)	$ (0.10)	$ (0.19)
Net income (loss) attributable to common shareholders/unitholders, Diluted	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ (0.05)	$ 0.03	$ (0.06)	$ (0.02)	$ (0.06)	$ (0.10)	$ (0.19)
Series C Preferred Stock [Member]
Preferred Units [Line Items]
Preferred shares, dividend rate (as a percent)									0.00%	7.50%
Series E Preferred Stock [Member]
Preferred Units [Line Items]
Preferred shares, dividend rate (as a percent)									6.90%
Series D Preferred Stock [Member]
Preferred Units [Line Items]
Preferred shares, dividend rate (as a percent)									0.00%	7.375%