SEGMENT INFORMATION - Unconsolidated Real Estate Ventures of Company's Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Investment in real estate ventures	$ 565,842		$ 552,494
Equity in income (loss) of real estate ventures	(13,588)	$ (6,167)
Philadelphia CBD
Segment Reporting Information [Line Items]
Investment in real estate ventures	468,642		450,136
Equity in income (loss) of real estate ventures	(9,613)	(3,259)
Metropolitan Washington, D.C.
Segment Reporting Information [Line Items]
Investment in real estate ventures	69,288		71,931
Equity in income (loss) of real estate ventures	(752)	(1,176)
Mid-Atlantic Office JV
Segment Reporting Information [Line Items]
Investment in real estate ventures	0		0
Equity in income (loss) of real estate ventures	0	190
MAP Venture
Segment Reporting Information [Line Items]
Investment in real estate ventures	(52,200)		(48,733)
Equity in income (loss) of real estate ventures	(3,223)	(1,922)
Austin, Texas
Segment Reporting Information [Line Items]
Investment in real estate ventures	80,112		$ 79,160
Equity in income (loss) of real estate ventures	$ 0	$ 0