REAL ESTATE INVESTMENTS - Summary of Property Dispositions (Details) $ in Thousands				3 Months Ended		6 Months Ended
	Jun. 28, 2022 USD ($)	Apr. 14, 2022 USD ($) a	Jan. 20, 2022 USD ($) a	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 28, 2022 a	Jun. 28, 2022 ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on disposition of real estate				$ 144	$ 68	$ 144	$ 142
Net gain on sale of undepreciated real estate				$ 4,127	$ 0	5,024	$ 1,993
Land | Gateway G & H
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | a			10.0
Sales Price			$ 1,600
Net gain on disposition of real estate			$ 897
Land | 25 M Street
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres | a		0.8
Sales Price		$ 29,675
Net gain on disposition of real estate		$ 3,436
Land | Gibbsboro Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on disposition of real estate	$ 700
Office/Land | Gibbsboro Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet/Acres								4.0	42,809
Sales Price	4,100
Net gain on disposition of real estate	$ 831
Office properties | Gibbsboro Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on disposition of real estate						$ 100