Organization of The Parent Company and The Operating Partnership (Textual) (Details)	3 Months Ended
	Mar. 31, 2020 a ft² parcel property
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties | property	94
Net rentable area (in square feet)	16,580,310
Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Areas of land held for development (in acres) | a	242.5
Area of land held for sale (in acres) | a	49.2
Area of additional undeveloped parcels of land with option to purchase (in acres) | a	55.5
Total potential development capacity (in square feet)	14,400,000
Parent Company | Land Parcel One
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company | Land Parcel Two
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company | Assets Held-for-sale
Organization of The Parent Company and The Operating Partnership [Line Items]
Total potential development capacity (in square feet)	300,000
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	1.8
Number of parcels of land | parcel	2
Wholly-owned Management Company Subsidiaries
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable area (in square feet)	24,100,000
Wholly-owned Management Company Subsidiaries | Wholly Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable area (in square feet)	16,600,000
Wholly-owned Management Company Subsidiaries | Partially Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable area (in square feet)	7,500,000
Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	99.40%