Schedule III - Summary of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 377,169
Initial Cost of Building & Improvements	1,602,518
Cost of Improvements Net of Retirements and Impairment Charges	1,226,674
Balance of Land and Land Held for Development	452,520
Balance of Building & Improvements and Construction in Progress	2,753,841
Accumulated Depreciation Balance	1,405,260	$ 1,308,427	$ 1,202,722
Current Encumbrance	851,283
Capital City Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	11,380
Initial Cost of Building & Improvements	65,575
Cost of Improvements Net of Retirements and Impairment Charges	61,069
Balance of Land and Land Held for Development	11,325
Balance of Building & Improvements and Construction in Progress	126,699
Accumulated Depreciation Balance	$ 61,580
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Cherry Hill Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 29,938
Initial Cost of Building & Improvements	185,611
Cost of Improvements Net of Retirements and Impairment Charges	270,201
Balance of Land and Land Held for Development	48,610
Balance of Building & Improvements and Construction in Progress	437,140
Accumulated Depreciation Balance	290,965
Current Encumbrance	$ 255,791
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Cumberland Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 8,711
Initial Cost of Building & Improvements	43,889
Cost of Improvements Net of Retirements and Impairment Charges	32,826
Balance of Land and Land Held for Development	9,842
Balance of Building & Improvements and Construction in Progress	75,584
Accumulated Depreciation Balance	36,962
Current Encumbrance	$ 39,146
Date of Acquisition/ Construction	2005
Life of Depre- ciation	40 years
Dartmouth Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 7,015
Initial Cost of Building & Improvements	28,328
Cost of Improvements Net of Retirements and Impairment Charges	57,080
Balance of Land and Land Held for Development	8,286
Balance of Building & Improvements and Construction in Progress	84,137
Accumulated Depreciation Balance	51,347
Current Encumbrance	$ 55,318
Date of Acquisition/ Construction	1998
Life of Depre- ciation	40 years
Exton Square Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 19,976
Initial Cost of Building & Improvements	103,955
Cost of Improvements Net of Retirements and Impairment Charges	(83,277)
Balance of Land and Land Held for Development	15,989
Balance of Building & Improvements and Construction in Progress	24,665
Accumulated Depreciation Balance	$ 14,526
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Francis Scott Key Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 9,786
Initial Cost of Building & Improvements	47,526
Cost of Improvements Net of Retirements and Impairment Charges	40,983
Balance of Land and Land Held for Development	9,442
Balance of Building & Improvements and Construction in Progress	88,853
Accumulated Depreciation Balance	49,342
Current Encumbrance	$ 59,490
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Jacksonville Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 9,188
Initial Cost of Building & Improvements	47,139
Cost of Improvements Net of Retirements and Impairment Charges	38,714
Balance of Land and Land Held for Development	9,913
Balance of Building & Improvements and Construction in Progress	85,128
Accumulated Depreciation Balance	$ 46,540
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Magnolia Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 6,229
Initial Cost of Building & Improvements	42,302
Cost of Improvements Net of Retirements and Impairment Charges	60,364
Balance of Land and Land Held for Development	12,588
Balance of Building & Improvements and Construction in Progress	96,307
Accumulated Depreciation Balance	$ 57,520
Date of Acquisition/ Construction	1998
Life of Depre- ciation	40 years
Monroe Land
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 262
Cost of Improvements Net of Retirements and Impairment Charges	$ (262)
Date of Acquisition/ Construction	2006
Life of Depre- ciation	10 years
Moorestown Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 10,934
Initial Cost of Building & Improvements	62,995
Cost of Improvements Net of Retirements and Impairment Charges	113,038
Balance of Land and Land Held for Development	23,058
Balance of Building & Improvements and Construction in Progress	163,909
Accumulated Depreciation Balance	$ 88,977
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Patrick Henry Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 16,075
Initial Cost of Building & Improvements	86,643
Cost of Improvements Net of Retirements and Impairment Charges	54,763
Balance of Land and Land Held for Development	16,398
Balance of Building & Improvements and Construction in Progress	141,083
Accumulated Depreciation Balance	81,741
Current Encumbrance	$ 84,924
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Plymouth Meeting Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 29,265
Initial Cost of Building & Improvements	58,388
Cost of Improvements Net of Retirements and Impairment Charges	158,560
Balance of Land and Land Held for Development	31,737
Balance of Building & Improvements and Construction in Progress	214,476
Accumulated Depreciation Balance	$ 118,337
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
The Mall at Prince Georges
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 18,156
Initial Cost of Building & Improvements	57,686
Cost of Improvements Net of Retirements and Impairment Charges	66,317
Balance of Land and Land Held for Development	11,805
Balance of Building & Improvements and Construction in Progress	130,354
Accumulated Depreciation Balance	$ 75,567
Date of Acquisition/ Construction	1998
Life of Depre- ciation	40 years
Springfield Town Center
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 119,912
Initial Cost of Building & Improvements	353,551
Cost of Improvements Net of Retirements and Impairment Charges	23,651
Balance of Land and Land Held for Development	119,911
Balance of Building & Improvements and Construction in Progress	377,203
Accumulated Depreciation Balance	$ 95,571
Date of Acquisition/ Construction	2015
Life of Depre- ciation	40 years
Swedes Square Land
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 189
Cost of Improvements Net of Retirements and Impairment Charges	36
Balance of Land and Land Held for Development	$ 225
Date of Acquisition/ Construction	2004
Valley Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 8,325
Initial Cost of Building & Improvements	57,931
Cost of Improvements Net of Retirements and Impairment Charges	84,737
Balance of Land and Land Held for Development	26,991
Balance of Building & Improvements and Construction in Progress	124,002
Accumulated Depreciation Balance	$ 59,345
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Valley View Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 5,869
Initial Cost of Building & Improvements	46,326
Cost of Improvements Net of Retirements and Impairment Charges	(52,131)
Balance of Land and Land Held for Development	826
Balance of Building & Improvements and Construction in Progress	890
Accumulated Depreciation Balance	66
Current Encumbrance	$ 27,213
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Viewmont Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 12,505
Initial Cost of Building & Improvements	61,519
Cost of Improvements Net of Retirements and Impairment Charges	48,560
Balance of Land and Land Held for Development	12,605
Balance of Building & Improvements and Construction in Progress	109,979
Accumulated Depreciation Balance	59,046
Current Encumbrance	$ 66,718
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Willow Grove Park
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 26,748
Initial Cost of Building & Improvements	131,189
Cost of Improvements Net of Retirements and Impairment Charges	112,282
Balance of Land and Land Held for Development	39,756
Balance of Building & Improvements and Construction in Progress	230,463
Accumulated Depreciation Balance	120,100
Current Encumbrance	$ 148,883
Date of Acquisition/ Construction	2003
Life of Depre- ciation	40 years
Woodland Mall
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost of Land	$ 26,706
Initial Cost of Building & Improvements	121,965
Cost of Improvements Net of Retirements and Impairment Charges	139,163
Balance of Land and Land Held for Development	44,865
Balance of Building & Improvements and Construction in Progress	242,969
Accumulated Depreciation Balance	97,728
Current Encumbrance	$ 113,800
Date of Acquisition/ Construction	2005
Life of Depre- ciation	40 years