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INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - evo at Cira Centre South Venture (Details) $ in Thousands |  | 12 Months Ended
--- | --- | ---
Jan. 10, 2018 USD ($) housing_unit | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |
Proceeds from real estate venture sales |  | $ 9,730 | $ 60,346 | $ 145,416
Net gain on real estate venture transactions |  | $ 11,639 | $ 142,233 | $ 80,526
Evo At Cira Disposition [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Sale of ownership interest percentage | 50.00% |  |  |
Number of property units sold | housing_unit | 345 |  |  |
Sales Price | $ 197,500 |  |  |
Proceeds from real estate venture sales | 43,000 |  |  |
Cost of equity method investment | 17,300 |  |  |
Net gain on real estate venture transactions | 25,700 |  |  |
Philadelphia [Member] | Pennsylvania | Evo At Cira Disposition [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Development costs contemplated debt financing | $ 110,900 |  |  |

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