ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP - Narrative (Details)	6 Months Ended
	Jun. 30, 2023 ft² a property parcel
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of real estate properties | property	76
Rentable Square Feet	13,404,886
Unconsolidated Properties | Unconsolidated Real Estate Ventures
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of real estate properties | property	12
Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Rentable Square Feet	11,800,000
Areas of land held for development (in acres) | a	152.1
Lease agreement term	99 years
Area of additional undeveloped parcels of land with option to purchase (in acres) | a	55.1
Parent Company | Parcel of land
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company | Leashold Interest Land
Organization of The Parent Company and The Operating Partnership [Line Items]
Areas of land held for development (in acres) | a	0.8
Number of parcels of land | parcel	1
Wholly-owned Management Company Subsidiaries
Organization of The Parent Company and The Operating Partnership [Line Items]
Rentable Square Feet	22,800,000
Wholly-owned Management Company Subsidiaries | Wholly Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Rentable Square Feet	13,400,000
Wholly-owned Management Company Subsidiaries | Partially Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Rentable Square Feet	9,400,000
Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	99.70%