REAL ESTATE INVESTMENTS - Schedule of Acquired Properties (Details) $ in Thousands						12 Months Ended
	Apr. 29, 2022 USD ($)	Jan. 21, 2022 USD ($) a	Nov. 30, 2020 USD ($) ft²	Nov. 05, 2020 USD ($) ft²	Feb. 27, 2020 USD ($) a	Dec. 31, 2022 USD ($) ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Apr. 29, 2022 ft²	Apr. 29, 2022 a
Business Acquisition [Line Items]
Purchase price						$ 3,446	$ 0	$ 41,950
Area of real estate property | ft²						13,578,188
Land | 631 Park Avenue
Business Acquisition [Line Items]
Land area | a		3.3
Purchase price		$ 3,650
Land | 3151 Market Street
Business Acquisition [Line Items]
Land area									0.8	0.8
Purchase price	$ 27,349
Lease agreement term (in years)	99 years
Prepaid Rent	$ 19,500
Area of real estate property | ft²									500,000
Land | 155 King of Prussia Road
Business Acquisition [Line Items]
Land area | a					7.75
Purchase price					$ 11,250
Land | Schuylkill Yards Project
Business Acquisition [Line Items]
Area of real estate property | ft²									200,000
Operating Lease Costs, Capitalized	$ 7,800
Office | 1505-11 Race Street
Business Acquisition [Line Items]
Rentable Square Feet | ft²				119,763
Purchase price				$ 9,700
Office | 250 King of Prussia Road
Business Acquisition [Line Items]
Rentable Square Feet | ft²			169,843
Purchase price			$ 20,250