SEGMENT INFORMATION - Net Operating Income of Company's Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Total revenue	$ 126,484	$ 129,227
Operating expenses	(47,414)	(50,835)
Net operating income	79,070	78,392
Operating Segments | Philadelphia CBD
Segment Reporting Information [Line Items]
Total revenue	55,988	56,227
Operating expenses	(19,882)	(20,586)
Net operating income	36,106	35,641
Operating Segments | Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Total revenue	32,019	32,771
Operating expenses	(9,359)	(9,779)
Net operating income	22,660	22,992
Operating Segments | Austin, Texas
Segment Reporting Information [Line Items]
Total revenue	23,255	25,237
Operating expenses	(9,013)	(11,294)
Net operating income	14,242	13,943
Operating Segments | Other
Segment Reporting Information [Line Items]
Total revenue	10,968	9,389
Operating expenses	(5,462)	(5,412)
Net operating income	5,506	3,977
Corporate
Segment Reporting Information [Line Items]
Total revenue	4,254	5,603
Operating expenses	(3,698)	(3,764)
Net operating income	$ 556	$ 1,839