REAL ESTATE INVESTMENTS - Narratives (Details) $ in Thousands			3 Months Ended		9 Months Ended
	Jul. 29, 2022 USD ($)	Jul. 14, 2022 USD ($) ft²	Sep. 30, 2022 USD ($) ft²	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) ft²	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Real Estate Properties [Line Items]
Net gain on disposition of real estate			$ 8,669	$ 0	$ 8,813	$ 142
Rentable Square Feet | ft²			13,664,209		13,664,209
Investment in real estate ventures			$ 546,935		$ 546,935		$ 411,110
3151 Market Street | Land
Real Estate Properties [Line Items]
Rentable Square Feet | ft²		500,000
3151 Market Street | Leasehold Interest
Real Estate Properties [Line Items]
Net gain on disposition of real estate		$ 2,583
Lease agreement term		99 years
11501 Burnet Road | Land
Real Estate Properties [Line Items]
Net gain on disposition of real estate	$ 8,312
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Real Estate Properties [Line Items]
Net gain on disposition of real estate			$ 8,669	$ 0	$ 8,813	$ 142