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REAL ESTATE INVESTMENTS - Acquisitions Narrative (Details) $ in Thousands |  |  |  |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 19, 2018 USD ($) ft² | Dec. 11, 2018 USD ($) ft² property | Jun. 29, 2018 USD ($) ft² | Mar. 22, 2018 USD ($) ft² | Jan. 05, 2018 USD ($) ft² | Dec. 31, 2020 USD ($) ft² property | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 21, 2020 | Nov. 05, 2020 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Number of properties | property |  |  |  |  |  | 82 |  |  |  |
Area of real estate property | ft² |  |  |  |  |  | 13,852,464 |  |  |  |
Net gain on real estate venture transactions |  |  |  |  |  | $ 75 | $ 11,639 | $ 142,233 |  |
Gain on promoted interest in unconsolidated real estate venture |  |  |  |  |  | 0 | 0 | 28,283 |  |
Prepaid leasehold interests in land held for development, net |  |  |  |  |  | 39,185 | 39,592 |  |  |
Sale of ownership interest percentage |  |  |  |  |  |  |  |  | 60.00% |
Revenue |  |  |  |  |  | 534,852 | 580,417 | 544,345 |  |
Net income (loss) |  |  |  |  |  | $ 305,527 | $ 34,267 | 134,518 |  |
Seven Tower Bridge |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Sale of ownership interest percentage |  |  |  |  | 20.00% |  |  |  |  |
1505-11 Race Street |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Transaction costs capitalized |  |  |  |  |  |  |  |  |  | $ 300
Quarry Lake II |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Rentable square feet | ft² | 120,559 |  |  |  |  |  |  |  |  |
Gross purchase value of office property | $ 39,500 |  |  |  |  |  |  |  |  |
Mortgage debt assumed repaid at settlement | 0 |  |  |  |  |  |  |  |  |
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Working Capital Assumed | 368 |  |  |  |  |  |  |  |  |
Aggregate cash payment | $ 39,037 |  |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  | 100 |  |
Net income (loss) |  |  |  |  |  |  |  | 100 |  |
DRA Austin Venture |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Gross purchase value of office property |  | $ 535,100 |  |  |  |  |  |  |  |
Ownership percentage |  | 50.00% |  |  |  |  |  |  |  |
Number of properties | property |  | 12 |  |  |  |  |  |  |  |
Area of real estate property | ft² |  | 1,570,123 |  |  |  |  |  |  |  |
Net gain on real estate venture transactions |  | $ 103,800 |  |  |  |  |  |  |  |
Gain on promoted interest in unconsolidated real estate venture |  | 28,300 |  |  |  |  |  |  |  |
Investment in real estate venture |  | 14,600 |  |  |  |  |  |  |  |
Mortgage debt assumed repaid at settlement |  | 115,461 |  |  |  |  |  |  |  |
Credit settlement for notes receivable provided to venture |  | 130,700 |  |  |  |  |  |  |  |
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Working Capital Assumed |  | 24,865 |  |  |  |  |  |  |  |
Aggregate cash payment |  | $ 117,348 |  |  |  |  |  |  |  |
Percentage of ownership interests |  | 50.00% |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  | 3,400 |  |
Net income (loss) |  |  |  |  |  |  |  | 1,300 |  |
3025 JFK Boulevard |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Lease agreement term |  |  | 99 years |  |  |  |  |  |  |
Acres | ft² |  |  | 1 |  |  |  |  |  |  |
Prepaid leasehold interests in land held for development, net |  |  | $ 15,000 |  |  |  |  |  |  |
Capitalized transaction costs |  |  | 300 |  |  |  |  |  |  |
Leasehold valuation credit |  |  | 5,600 |  |  |  |  |  |  |
3001-3003 and 3025 JFK Boulevard |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Leasehold valuation credit applied to development |  |  | $ 2,400 |  |  |  |  |  |  |
Minimum floor area ratio required for realization of credit (sq. feet) | ft² |  |  | 1,200,000 |  |  |  |  |  |  |
Remaining leasehold valuation credit |  |  | $ 3,200 |  |  |  |  |  |  |
Reimbursable leasehold valuation credit |  |  | $ 3,200 |  |  |  |  |  |  |
3001-3003 JFK Boulevard |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Lease agreement term |  |  |  | 99 years |  |  |  |  |  |
Acres | ft² |  |  |  | 1 |  |  |  |  |  |
Prepaid leasehold interests in land held for development, net |  |  |  | $ 24,600 |  |  |  |  |  |
Capitalized transaction costs |  |  |  | $ 300 |  |  |  |  |  |
Four Tower Bridge |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership percentage |  |  |  |  | 35.00% |  |  |  |  |
Area of real estate property | ft² |  |  |  |  | 86,021 |  |  |  |  |
Mortgage debt assumed repaid at settlement |  |  |  |  | $ 0 |  |  |  |  |
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Working Capital Assumed |  |  |  |  | (1,379) |  |  |  |  |
Aggregate cash payment |  |  |  |  | $ 0 |  |  |  |  |
Percentage of ownership interest after non-monetary exchange transaction |  |  |  |  | 100.00% |  |  |  |  |
Real estate property debt |  |  |  |  | $ 9,700 |  |  |  |  |
Fair value of unencumbered acquisition related costs, to tangible and intangible assets and liabilities |  |  |  |  | $ 23,600 |  |  |  |  |
Revenue |  |  |  |  |  |  |  | 2,800 |  |
Net income (loss) |  |  |  |  |  |  |  | $ 300 |  |

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