SEGMENT INFORMATION - Schedule of Net Operating Income of Company's Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Total revenue	$ 131,782	$ 129,372	$ 383,612	$ 384,481
Operating expenses	(46,279)	(46,399)	(140,007)	(143,253)
Net operating income	85,503	82,973	243,605	241,228
Operating Segments | Philadelphia CBD
Segment Reporting Information [Line Items]
Total revenue	56,448	56,367	169,159	169,265
Operating expenses	(19,959)	(18,609)	(58,912)	(59,452)
Net operating income	36,489	37,758	110,247	109,813
Operating Segments | Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Total revenue	31,681	32,611	95,366	97,484
Operating expenses	(10,081)	(9,770)	(29,337)	(29,633)
Net operating income	21,600	22,841	66,029	67,851
Operating Segments | Austin, Texas
Segment Reporting Information [Line Items]
Total revenue	21,951	24,457	67,360	73,475
Operating expenses	(8,429)	(10,044)	(26,276)	(30,021)
Net operating income	13,522	14,413	41,084	43,454
Operating Segments | Other
Segment Reporting Information [Line Items]
Total revenue	10,430	10,295	31,706	28,572
Operating expenses	(5,076)	(5,526)	(15,670)	(15,788)
Net operating income	5,354	4,769	16,036	12,784
Corporate
Segment Reporting Information [Line Items]
Total revenue	11,272	5,642	20,021	15,685
Operating expenses	(2,734)	(2,450)	(9,812)	(8,359)
Net operating income	$ 8,538	$ 3,192	$ 10,209	$ 7,326