SEGMENT INFORMATION - Real Estate Investments, at Cost of Company's Reportable Segments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating properties	$ 3,374,780	$ 3,542,232	$ 3,617,240
Right of use asset - operating leases, net	18,412	19,031
Construction-in-progress	94,628	135,529
Land held for development	81,318	82,510
Prepaid leasehold interests in land held for development, net	27,762	27,762
Total Core Segments | Continuing Operations
Segment Reporting Information [Line Items]
Operating properties	3,097,025	3,237,096
Philadelphia CBD | Continuing Operations
Segment Reporting Information [Line Items]
Operating properties	1,556,696	1,534,893
Pennsylvania Suburbs | Continuing Operations
Segment Reporting Information [Line Items]
Operating properties	869,179	900,230
Austin, Texas | Continuing Operations
Segment Reporting Information [Line Items]
Operating properties	671,150	801,973
Other
Segment Reporting Information [Line Items]
Operating properties	$ 277,755	$ 305,136