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Amount of liability recognized arising from contingent consideration in a business combination.

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Fair value at acquisition-date of the equity interest in the acquiree held by the acquirer, immediately before the acquisition date for businesses combined in stages.

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Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

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Net rentable area for properties owned.

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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands			1 Months Ended	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands	Oct. 21, 2020 USD ($)	Apr. 02, 2015 USD ($)	Feb. 28, 2021 property	Dec. 31, 2021 USD ($)	Jul. 23, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2004 ft²
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness				$ 961,509		$ 963,018
Limited payment guarantee, percent of principle balance (up to)					25.00%
Commerce Square \| Preferred Equity Investment Obligation
Property Subject to or Available for Operating Lease [Line Items]
Other commitments				20,000
Amount committed to date				2,100
3025 JFK Venture
Property Subject to or Available for Operating Lease [Line Items]
Construction loan amount				186,700	$ 186,700
Natural Disasters and Other Casualty Events
Property Subject to or Available for Operating Lease [Line Items]
Number of properties damaged \| property			1
Write-off of fixed assets				1,200
Restoration liability				7,200
Business interruption costs				3,900
Insurance proceeds				15,300
Natural Disasters and Other Casualty Events \| Other Income
Property Subject to or Available for Operating Lease [Line Items]
Insurance proceeds				3,000
Natural Disasters and Other Casualty Events \| Accounts Payable and Accrued Liabilities
Property Subject to or Available for Operating Lease [Line Items]
Restoration liability				1,900
Unconsolidated Real Estate Ventures
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness				961,500
Two Logan Square
Property Subject to or Available for Operating Lease [Line Items]
Rentable square feet \| ft²							708,844
Settlement liabilities				600
Two Logan Square \| Secured Debt
Property Subject to or Available for Operating Lease [Line Items]
Repayments of long-term debt	$ 79,800
618 Market Street
Property Subject to or Available for Operating Lease [Line Items]
Contingent consideration, liability		$ 2,000
Fair value of contingent consideration		1,600
Interest expense		$ 2,000
Schuylkill Yards Project
Property Subject to or Available for Operating Lease [Line Items]
Other commitments				7,000
Estimated potential additional contribution obligation				$ 2,400