REAL ESTATE INVESTMENTS - Schedule of Office Properties Sold (Details) $ in Thousands																	12 Months Ended
	Dec. 20, 2024 USD ($) a	Nov. 18, 2024 USD ($) ft²	Sep. 30, 2024 USD ($) a	Sep. 26, 2024 USD ($) ft²	Dec. 27, 2023 USD ($) a	Dec. 07, 2023 USD ($) a	Dec. 01, 2023 USD ($) ft²	Oct. 31, 2023 USD ($) ft²	Aug. 04, 2023 USD ($) ft²	Nov. 22, 2022 USD ($) ft²	Sep. 30, 2022 USD ($)	Jul. 29, 2022 USD ($) a	Jul. 14, 2022 USD ($) a ft²	Jun. 28, 2022 USD ($)	Apr. 14, 2022 USD ($) a	Jan. 20, 2022 USD ($) a	Dec. 31, 2024 USD ($) ft²	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jan. 30, 2023 ft²	Jun. 28, 2022 ft²	Jun. 28, 2022 a
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain/(Loss) on Sale																	$ 2,297	$ 7,736	$ 17,677
Provision for impairment																	$ 44,655	$ 131,573	4,663
Area of real estate property | ft²																	12,098,843
Recognized a provision for impairment							$ 16,700
Plymouth Meeting Executive Center | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Seller financing amount																	$ 15,500
55 US Avenue | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Seller financing amount																	4,400
55 US Avenue and One and Two Barton Skyway | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Provision for impairment																	$ 21,100
Land | 55 US Avenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a			11
Sales Price			$ 6,466
Gain/(Loss) on Sale			$ 0
Land | Dabney East
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a					11.6
Sales Price					$ 1,600
Gain/(Loss) on Sale					$ 430
Land | Byberry
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a						50.0
Sales Price						$ 9,641
Gain/(Loss) on Sale						$ 3,960
Land | 11501 Burnett Road
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a												4.7
Sales Price												$ 32,513
Gain/(Loss) on Sale												$ 8,340
Land | 25 M Street
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a															0.8
Sales Price															$ 29,675
Gain/(Loss) on Sale											$ 400				$ 3,836
Land | Gateway G & H
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a																10.0
Sales Price																$ 1,600
Gain/(Loss) on Sale																$ 897
Land | Gibbsboro Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain/(Loss) on Sale																			700
Land | 3151 Market Street
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property | ft²													500,000
Land | 11501 Burnet Road
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a												4.7
Sales Price												$ 32,500
Gain/(Loss) on Sale												$ 8,300
Office Properties | Plymouth Meeting Executive Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | ft²				521,288
Sales Price				$ 65,500
Gain/(Loss) on Sale				$ 0
Office Properties | One and Two Barton Skyway
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | ft²		390,963
Sales Price		$ 107,900
Gain/(Loss) on Sale		$ 0
Office Properties | 8521 Leesburg Pike
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | ft²							150,897
Sales Price							$ 11,000
Gain/(Loss) on Sale							$ 0
Office Properties | Three Barton Skyway
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | ft²									173,302
Sales Price									$ 53,250
Gain/(Loss) on Sale									$ 0
Office Properties | 200 Barr Harbor Drive
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | ft²										86,000
Sales Price										$ 30,500
Gain/(Loss) on Sale										$ 8,740
Office Properties | Gibbsboro Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain/(Loss) on Sale																			$ 100
Retail | 200 N. Radnor Chester Road
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | ft²								17,884
Sales Price								$ 14,200
Gain/(Loss) on Sale								$ 7,735
Leasehold Interest | 3151 Market Street
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a													0.8
Sales Price													$ 30,394
Gain/(Loss) on Sale													2,583
Leasehold Interest | 3151 Market Street
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | ft²																				200,000
Sales Price													30,400
Gain/(Loss) on Sale													$ 2,600
Lease agreement term (in years)													99 years
Office/Land | Gibbsboro Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area																					42,809	4.0
Sales Price														$ 4,100
Gain/(Loss) on Sale														$ 831
Parking Lot | Dabney Land Westwood
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land area | a	11
Sales Price	$ 8,500
Gain/(Loss) on Sale	$ 2,297