INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Mid-Atlantic Office JV (Details)	Dec. 21, 2020 USD ($) ft² property	Mar. 31, 2024 USD ($) property	Dec. 31, 2023 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property		72
Investment in real estate ventures		$ 565,842,000	$ 552,494,000
Philadelphia CBD
Schedule of Equity Method Investments [Line Items]
Investment in real estate ventures		468,642,000	450,136,000
Other
Schedule of Equity Method Investments [Line Items]
Investment in real estate ventures		$ 69,288,000	$ 71,931,000
Mid-Atlantic Office Venture
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	40.00%
Joint venture, funding from debt	$ 147,400,000
Proceeds from issuance of secured debt	$ 120,800,000
Mid-Atlantic Office Venture | Mid-Atlantic Office JV Loan | Secured Overnight Financing Rate (SOFR)
Schedule of Equity Method Investments [Line Items]
Basis spread on interest rate (as percent)	3.25%
Office Properties | Mid-Atlantic Office Venture
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property	12
Rentable area (in square feet) | ft²	1,128,645
Disposal group, including discontinued operation, consideration	$ 192,900,000
Investment in real estate ventures	$ 0
Office Properties | Mid-Atlantic Office Venture | Philadelphia CBD
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property	9
Office Properties | Mid-Atlantic Office Venture | Other
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property	3