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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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Net rentable area for properties owned.

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INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Brandywine - AI Venture (Details) $ in Thousands		12 Months Ended
	Nov. 09, 2021 USD ($) ft²	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) ft²
Schedule of Equity Method Investments [Line Items]
Net gain on real estate venture transactions		$ 26,718	$ 2,973	$ 75
Impairment of properties held for use		$ 4,700
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]					Equity in loss of unconsolidated real estate ventures
Fairview Properties \| Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Provision for impairment on assets held for sale			1,400
Impairment of properties held for use					$ 5,600
Fairview Properties \| Brandywine - AI Venture LLC \| Brandywine Realty Trust
Schedule of Equity Method Investments [Line Items]
Provision for impairment on assets held for sale			$ 700
Impairment of properties held for use					$ 2,800
Falls Church, Virginia \| Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Rentable square feet \| ft²	183,618				180,659
Aggregate sales price	$ 27,600
Gross proceeds from sale	12,600
Net gain on real estate venture transactions	$ 3,000				$ 2,200
Debt, net					$ 26,000