Basis of Presentation (Textual) (Details)		3 Months Ended				6 Months Ended
	Mar. 15, 2017 USD ($) ft²	Jun. 30, 2019 USD ($) $ / shares		Mar. 31, 2019 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Jun. 30, 2019 USD ($) Acquisition Ground $ / shares		Jun. 30, 2018 USD ($) $ / shares	Jan. 15, 2024 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Basis Of Presentation [Line Items]
Number of acquisitions for which adjustments have been made to correct errors related to of purchase price allocation | Acquisition						2
Net income attributable to Brandywine Realty Trust		$ 6,205,000			$ 12,747,000	$ 10,728,000		$ 56,817,000
Diluted income per Common Share | $ / shares		$ 0.03			$ 0.07	$ 0.06		$ 0.31
Basic income per Common Share | $ / shares		$ 0.03			$ 0.07	$ 0.06		$ 0.32
Direct financing leases		$ 0				$ 0
Operating leases expiration dates extending						The operating leases have various expiration dates.
Cumulative effect of accounting change				$ (5,336,000)
Number of long-term ground leases | Ground						6
Right of use asset - operating leases		22,001,000	[1]			$ 22,001,000	[1]			$ 22,400,000	$ 0
Lease liability - operating leases		$ 22,453,000				22,453,000				$ 22,400,000	$ 0
Proceeds from the sale of properties						5,523,000		$ 16,771,000
Philadelphia Marine Center (Marine Piers) [Member]
Basis Of Presentation [Line Items]
Rentable Square Feet | ft²	181,900
Sales Price	$ 21,400,000
Payment by cash on purchases	12,000,000.0
Proceeds from the sale of properties	11,200,000
Balance payment on purchase price	$ 9,400,000								$ 9,400,000
Date of second installment payment	Jan. 31, 2020
Uncollectible Leases [Member]
Basis Of Presentation [Line Items]
Cumulative effect of accounting change						$ (700,000)
Error Corrections and Prior Period Adjustments [Member]
Basis Of Presentation [Line Items]
Net income attributable to Brandywine Realty Trust				$ 517,000	$ (260,000)			$ (520,000)
Diluted income per Common Share | $ / shares								$ (0.01)
Basic income per Common Share | $ / shares				$ 0.01
Reversal of Out of Period Adjustment [Member]
Basis Of Presentation [Line Items]
Net income attributable to Brandywine Realty Trust				$ 777,000
Reversal of Out of Period Adjustment Offset [Member]
Basis Of Presentation [Line Items]
Net income attributable to Brandywine Realty Trust				$ (260,000)

[1] On January 1, 2019, as a result of the adoption of Topic 842, Leases, the Company recognized operating ground leases for which it is a lessee on its consolidated balance sheets for the period ended March 31, 2019. See Note 2, “Basis of Presentation,” for further information.