SEGMENT INFORMATION - Unconsolidated Real Estate Ventures of Company's Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Investment in real estate ventures	$ 680,136		$ 680,136		$ 552,494
Equity in income (loss) of real estate ventures	(14,507)	$ (7,598)	(28,095)	$ (13,765)
Philadelphia CBD
Segment Reporting Information [Line Items]
Investment in real estate ventures	501,579		501,579		450,136
Equity in income (loss) of real estate ventures	(10,223)	(4,412)
Metropolitan Washington, D.C.
Segment Reporting Information [Line Items]
Investment in real estate ventures	94,834		94,834		71,931
Equity in income (loss) of real estate ventures	(941)	(1,414)
Mid-Atlantic Office JV
Segment Reporting Information [Line Items]
Investment in real estate ventures	0		0		0
Equity in income (loss) of real estate ventures	0	223
MAP Venture
Segment Reporting Information [Line Items]
Investment in real estate ventures	0		0		(48,733)
Equity in income (loss) of real estate ventures	(3,339)	(1,995)
Austin, Texas
Segment Reporting Information [Line Items]
Investment in real estate ventures	83,723		$ 83,723		$ 79,160
Equity in income (loss) of real estate ventures	$ (4)	$ 0