Organization of The Parent Company and The Operating Partnership (Textual) (Details)	3 Months Ended
	Mar. 31, 2019 ft² a property Parcel
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	96
Net Rentable Square Feet	16,922,019
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Undeveloped Parcels of Land | a	234.7
Undeveloped Land Held for Sale | a	35.2
Area of Additional Undeveloped Parcels of Land With Option to Purchase | a	55.5
Total Potential Development Capacity	14,200,000
Parent Company [Member] | Land Parcel One [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company [Member] | Land Parcel Two [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company [Member] | Assets Held-for-sale [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Total Potential Development Capacity	200,000
Wholly-owned Management Company Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	24,900,000
Wholly-owned Management Company Subsidiaries [Member] | Wholly Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	16,900,000
Wholly-owned Management Company Subsidiaries [Member] | Partially Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	8,000,000.0
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	1
Redevelopment Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	3
Leashold Interest Land [Member] | Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Parcels | Parcel	2
Undeveloped Parcels of Land Held | a	1.8
Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	99.40%