Basis of Presentation - Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating properties	$ 4,030,605		$ 3,951,719
Accumulated depreciation	(940,833)		(885,407)
Operating real estate investments, net	3,111,773		3,066,312
Total assets	4,048,474		4,076,976
Additional Paid-in Capital	3,188,239		3,200,312
Cumulative Earnings	781,017		775,625
Total Brandywine Realty Trust's equity	1,717,819		1,798,827
Noncontrolling interests	11,846		12,201
Total beneficiaries' equity	1,729,665	$ 1,760,463	1,811,028	$ 1,830,525	$ 1,847,251	$ 1,826,870
Total liabilities and beneficiaries' equity	4,048,474		4,076,976
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating properties	4,030,605		3,951,719
Accumulated depreciation	(940,833)		(885,407)
Operating real estate investments, net	3,111,773		3,066,312
Total assets	4,048,474		4,076,976
General Partnership Capital	1,715,685		1,791,591
Total Brandywine Operating Partnership, L.P.'s equity	1,713,181		1,796,316
Total partners' equity	1,715,445	$ 1,745,042	1,798,508	$ 1,805,756	$ 1,824,205	$ 1,799,955
Total liabilities and beneficiaries' equity	$ 4,048,474		4,076,976
As Previously Reported [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating properties			3,953,319
Accumulated depreciation			(865,462)
Operating real estate investments, net			3,087,857
Total assets			4,098,521
Additional Paid-in Capital			3,200,850
Cumulative Earnings			796,513
Total Brandywine Realty Trust's equity			1,820,253
Noncontrolling interests			12,320
Total beneficiaries' equity			1,832,573
Total liabilities and beneficiaries' equity			4,098,521
As Previously Reported [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating properties			3,953,319
Accumulated depreciation			(865,462)
Operating real estate investments, net			3,087,857
Total assets			4,098,521
General Partnership Capital			1,813,136
Total Brandywine Operating Partnership, L.P.'s equity			1,817,861
Total partners' equity			1,820,053
Total liabilities and beneficiaries' equity			4,098,521
Adjustments [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating properties			(1,600)
Accumulated depreciation			(19,945)
Operating real estate investments, net			(21,545)
Total assets			(21,545)
Additional Paid-in Capital			(538)
Cumulative Earnings			(20,888)
Total Brandywine Realty Trust's equity			(21,426)
Noncontrolling interests			(119)
Total beneficiaries' equity			(21,545)
Total liabilities and beneficiaries' equity			(21,545)
Adjustments [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating properties			(1,600)
Accumulated depreciation			(19,945)
Operating real estate investments, net			(21,545)
Total assets			(21,545)
General Partnership Capital			(21,545)
Total Brandywine Operating Partnership, L.P.'s equity			(21,545)
Total partners' equity			(21,545)
Total liabilities and beneficiaries' equity			$ (21,545)