Schedule III - Real Estate and Accumulated Depreciation (Reconciliations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the Beginning of the Year	$ 3,474,109	$ 4,006,459	$ 3,951,719
Additions:
Acquisitions	0	9,722	0
Capital expenditures and assets placed into service	134,931	113,221	145,378
Less:
Dispositions/impairments/placed into redevelopment	(82,247)	(619,086)	(50,792)
Retirements	(54,191)	(36,207)	(39,846)
Balance at the end of the year	3,472,602	3,474,109	4,006,459
Operating properties	3,472,602	3,474,109	4,006,459
Tax basis of assets, cost for income tax purposes	3,100,000	2,900,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year	896,561	973,318	885,407
Additions:
Depreciation expense	136,171	138,822	144,131
Less:
Dispositions/impairments/placed into redevelopment	(24,440)	(182,526)	(16,783)
Retirements	(50,842)	(33,053)	(39,437)
Balance at the end of the year	957,450	896,561	973,318
Per consolidated balance sheet	957,450	896,561	$ 973,318
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Less:
Operating properties	3,472,602	3,474,109
Tax basis of assets, cost for income tax purposes	3,100,000	2,900,000
Less:
Per consolidated balance sheet	$ 957,450	$ 896,561
Leashold Interest Land
Less:
Lease agreement term	99 years
Maximum
Less:
Useful life	55 years