FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS (UNITED DOMINION REALTY, L.P.) (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2020	Dec. 31, 2019
Debt instruments - fair value
Transfer between the levels	$ 0
Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Total assets	155,964	$ 153,656
Total liabilities	4,793,871	4,731,595
Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Total assets	166,017	160,203
Total liabilities	5,059,174	4,853,337
Interest rate contracts \| Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Derivative Asset Designated as Hedging Instrument, Fair Value	8	6
Interest rate contracts \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Derivative Asset Designated as Hedging Instrument, Fair Value	8	6
Level 2 \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Total assets	8	6
Total liabilities	2,414	142
Level 2 \| Interest rate contracts \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Derivative Asset Designated as Hedging Instrument, Fair Value	8	6
Level 3 \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Total assets	166,009	160,197
Total liabilities	5,056,760	4,853,195
United Dominion Realty L.P. \| Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Total assets	8
Total liabilities	755,119	736,733
United Dominion Realty L.P. \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Total assets	8
Total liabilities	760,628	736,209
United Dominion Realty L.P. \| Mortgages Note Payable \| Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Fair value		72,500
United Dominion Realty L.P. \| Mortgages Note Payable \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value		71,976
United Dominion Realty L.P. \| Interest rate contracts \| Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Derivative Asset Designated as Hedging Instrument, Fair Value	8
United Dominion Realty L.P. \| Interest rate contracts \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Derivative Asset Designated as Hedging Instrument, Fair Value	8
United Dominion Realty L.P. \| Notes payable due to the General Partner \| Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Fair value	655,619	637,233
United Dominion Realty L.P. \| Notes payable due to the General Partner \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value	655,619	637,233
United Dominion Realty L.P. \| Level 2 \| Fair Value, Measurements, Recurring
Debt instruments - fair value
Total assets	8
United Dominion Realty L.P. \| Level 2 \| Interest rate contracts \| Fair Value, Measurements, Recurring
Debt instruments - fair value
Derivative Asset Designated as Hedging Instrument, Fair Value	8
United Dominion Realty L.P. \| Level 3 \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Total liabilities	760,628	736,209
United Dominion Realty L.P. \| Level 3 \| Mortgages Note Payable \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value		71,976
United Dominion Realty L.P. \| Level 3 \| Notes payable due to the General Partner \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value	655,619	637,233
Fixed Rate Debt \| United Dominion Realty L.P. \| Mortgages Note Payable \| Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Fair value	72,500
Fixed Rate Debt \| United Dominion Realty L.P. \| Mortgages Note Payable \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value	78,009
Fixed Rate Debt \| United Dominion Realty L.P. \| Level 3 \| Mortgages Note Payable \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value	78,009
Variable Rate Debt \| United Dominion Realty L.P. \| Tax-exempt secured notes payable \| Fair Value, Measurements, Recurring \| Carrying Amount
Debt instruments - fair value
Fair value	27,000	27,000
Variable Rate Debt \| United Dominion Realty L.P. \| Tax-exempt secured notes payable \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value	27,000	27,000
Variable Rate Debt \| United Dominion Realty L.P. \| Level 3 \| Tax-exempt secured notes payable \| Fair Value, Measurements, Recurring \| Fair Value
Debt instruments - fair value
Fair value	$ 27,000	$ 27,000

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

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-Publisher FASB
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Fair value of financial and nonfinancial obligations.

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