ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 a ft² parcel property managementCompany
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of real estate properties | property	72
Rentable square feet	13,011,094
Number of management companies | managementCompany	7
Leashold Interest Land
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term (in years)	99 years
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	12,100,000
Areas of land held for development (in acres) | a	141.6
Lease agreement term (in years)	99 years
Area of additional undeveloped parcels of land with option to purchase | a	5.1
Parent Company | Parcel of land
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term (in years)	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	22,400,000
Wholly-owned Management Company Subsidiaries | Wholly Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Rentable square feet	13,000,000
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%
BRSCO | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BMI | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BPI | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BBL | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BPM | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BBS | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BGCS | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%