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JOINT VENTURES AND PARTNERSHIPS - Commitments (Details) |  | 1 Months Ended | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Nov. 30, 2019 USD ($) community | Nov. 30, 2019 USD ($) item community | Nov. 30, 2019 USD ($) community | Nov. 30, 2019 USD ($) property community | Nov. 30, 2019 USD ($) community | Aug. 31, 2019 USD ($) home | May 31, 2019 USD ($) home community | Dec. 31, 2019 USD ($) community item | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Jul. 31, 2019 | Apr. 30, 2019 USD ($) home | Jan. 01, 2019 community | Sep. 30, 2018 USD ($) item | Aug. 31, 2018 USD ($) item
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Real estate owned |  |  |  |  |  |  |  | $ 12,602,101,000 | $ 10,196,159,000 |  |  |  |  |  |
Investment in unconsolidated entities |  |  |  |  |  |  |  |  | 585,490,000 |  |  |  |  |  |
Time to maintain percent occupancy to be considered a community |  |  |  |  |  |  |  | 3 months |  |  |  |  |  |  |
Number of land parcels | property |  |  |  | 4 |  |  |  |  |  |  |  |  |  |  |
Investment in unconsolidated joint ventures |  |  |  |  |  |  |  | $ 93,059,000 | 112,025,000 | $ 123,842,000 |  |  |  |  |
Gain on consolidation |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |
Long-term Debt |  |  |  |  |  |  |  | 4,707,524,000 | 3,547,787,000 |  |  |  |  |  |
Deferred fees from the sale of properties |  |  |  |  |  |  |  | 9,000,000.0 | 11,000,000.0 |  |  |  |  |  |
Joint venture management and other fees |  |  |  |  |  |  |  | $ 14,055,000 | $ 11,754,000 | $ 11,482,000 |  |  |  |  |
Type of revenue |  |  |  |  |  |  |  | udr:ManagementAndOtherFeesMember | udr:ManagementAndOtherFeesMember | udr:ManagementAndOtherFeesMember |  |  |  |  |
Management Service |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture management and other fees |  |  |  |  |  |  |  | $ 14,000,000.0 | $ 11,600,000 | $ 11,400,000 |  |  |  |  |
Joint Ventures and Partnerships |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  |  |  |  | $ 1,068,200,000 | 2,174,137,000 |  |  |  |  |  |
UDR/MetLife operating communities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
UDR's Ownership Interest | 50.00% | 50.00% | 50.00% | 50.00% | 50.00% |  |  |  |  |  |  |  |  |  |
Number of communities acquired | community |  |  |  |  | 10 |  |  | 10 |  |  |  |  |  |  |
Number of communities under development purchased | community |  |  |  |  | 1 |  |  | 1 |  |  |  |  |  |  |
Number of land parcels |  | 4 |  | 4 |  |  |  | 4 |  |  |  |  |  |  |
Total value of joint venture portion that was purchased | $ 1,100,000,000 | $ 1,100,000,000 | $ 1,100,000,000 | $ 1,100,000,000 | $ 1,100,000,000 |  |  |  |  |  |  |  |  |  |
Total value of joint venture that was purchased - UDR's share |  |  | 564,200,000 |  |  |  |  |  |  |  |  |  |  |  |
Value of Joint Venture Sold | $ 645,800,000 | $ 645,800,000 | 645,800,000 | $ 645,800,000 | $ 645,800,000 |  |  |  |  |  |  |  |  |  |
Sale value of joint venture |  |  | 645,800,000 |  |  |  |  |  |  |  |  |  |  |  |
Sale value of joint venture UDR's share |  |  | 322,900,000 |  |  |  |  |  |  |  |  |  |  |  |
Payment to acquire real estate |  |  | 109,200,000 |  |  |  |  |  |  |  |  |  |  |  |
Gain on consolidation |  |  | $ 114,900,000 |  |  |  |  | $ 131,500,000 |  |  |  |  |  |  |
Number of communities sold | community | 5 | 5 | 5 | 5 | 5 |  |  |  |  |  |  |  |  |  |
Ownership interest (percentage) |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |
UDR/MetLife II operating communities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Operating Communities Held Upon Closing Of Transactions | community | 7 |  |  |  |  |  |  |  |  |  |  |  |  |  |
UDR's Ownership Interest |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |
Number of communities acquired | community |  |  |  |  | 15 |  |  | 5 |  |  |  |  |  |  |
Gain on consolidation |  |  |  |  |  |  |  | $ 114,900,000 |  |  |  |  |  |  |
Unconsolidated Joint Venture Vitruvian Park |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  |  |  |  |  | 177,099,000 |  |  |  |  |  |
Unconsolidated Joint Venture UDR Met Life I Partnership |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  |  |  |  | 74,927,000 | 72,768,000 |  |  |  |  |  |
Unconsolidated Joint Venture UDR MetLife II Partnership |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  |  |  |  | 434,606,000 | 1,110,489,000 |  |  |  |  |  |
Unconsolidated Joint Venture Three Washington DC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
UDR's Ownership Interest |  |  |  |  |  | 100.00% |  |  |  |  | 30.00% |  |  |  |
Payment to acquire real estate |  |  |  |  |  | $ 184,000,000.0 |  |  |  |  |  |  |  |  |
Gain on consolidation |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |
Number of completed communities | community |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |
Number of communities sold | home |  |  |  |  |  | 292 |  |  |  |  |  |  |  |  |
Acquisition-related costs |  |  |  |  |  | $ 2,800,000 |  |  |  |  |  |  |  |  |
Reduction of carrying amount of real estate |  |  |  |  |  | $ 23,800,000 |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  |  |  |  |  | 167,559,000 |  |  |  |  |  |
Ownership interest (percentage) |  |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |
Unconsolidated Joint Venture Other MetLife |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  |  |  |  | 464,729,000 | 464,400,000 |  |  |  |  |  |
Preferred Equity Investment West Coast Development JV |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  |  |  |  | $ 93,938,000 | 181,822,000 |  |  |  |  |  |
Preferred Equity Investment Hillsboro Oregon |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
UDR's Ownership Interest |  |  |  |  |  |  |  | 49.00% |  |  |  |  |  |  |
Preferred Equity Investment 1641 Lincoln Santa Monica CA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in unconsolidated entities |  |  |  |  |  |  |  | $ 10,379,000 | 9,211,000 |  |  |  |  |  |
Income from investments |  |  |  |  |  |  |  | $ 1,169,000 | 406,000 |  |  |  |  |  |
Preferred return (as a percent) |  |  |  |  |  |  |  | 12.00% |  |  |  |  |  |  | 12.00%
Number of apartment homes |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 66
Equity Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 8,800,000
Preferred Equity Investment 1300 Fairmount Philadelphia, PA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in unconsolidated entities |  |  |  |  |  |  |  | $ 51,215,000 | 8,318,000 |  |  |  |  |  |
Income from investments |  |  |  |  |  |  |  | 3,098,000 | 159,000 |  |  |  |  |  |
Number of apartment homes | item |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 471
Equity Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 51,400,000
Preferred Equity Investment Essex Orlando, FL |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in unconsolidated entities |  |  |  |  |  |  |  | 14,804,000 | 9,940,000 |  |  |  |  |  |
Income from investments |  |  |  |  |  |  |  | $ 1,639,000 | $ 258,000 |  |  |  |  |  |
Preferred return (as a percent) |  |  |  |  |  |  |  | 12.50% |  |  |  |  |  | 12.50% |
Number of apartment homes | item |  |  |  |  |  |  |  |  |  |  |  |  |  | 330 |
Equity Investment |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 12,900,000 |
Operating Communities in Arlington, Virginia and Silver Spring, Maryland |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of communities sold | community |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |
Number of apartment homes | home |  |  |  |  |  |  | 368 |  |  |  |  |  |  |  |
Proceeds from sale of real estate |  |  |  |  |  |  | $ 118,300,000 |  |  |  |  |  |  |  |
Gain/(loss) on sales of real estate owned, net of tax |  |  |  |  |  |  | $ 10,600,000 |  |  |  |  |  |  |  |
Preferred Equity Investment Modera Lake Merritt, Oakland |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred return (as a percent) |  |  |  |  |  |  |  |  |  |  |  | 9.00% |  |  |
Number of apartment homes | home |  |  |  |  |  |  |  |  |  |  |  | 173 |  |  |
Equity Investment |  |  |  |  |  |  |  |  |  |  |  | $ 27,300,000 |  |  |
UDR/KFH joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of communities sold | community |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |
Maximum | Preferred Equity Investment 1300 Fairmount Philadelphia, PA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred return (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12.00%
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
UDR's Ownership Interest |  |  |  |  |  |  |  | 100.00% |  |  |  |  |  |  |
Minimum | Preferred Equity Investment 1300 Fairmount Philadelphia, PA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred return (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8.50%
Market Property LLC | Accounts Payable and Accrued Liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint Ventures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in unconsolidated entities |  |  |  |  |  |  |  | $ 2,800,000 |  |  |  |  |  |  |

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