DERIVATIVES AND HEDGING ACTIVITY - Effectiveness (UNITED DOMINION REALTY, L.P.) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivatives and hedging activity
Estimated additional accumulated other comprehensive Income/(Loss) transferred to interest expense	$ 3,900		$ 3,900
Total amount of Interest expense presented on the Consolidated Statements of Operations	38,597	$ 34,417	77,914	$ 67,959
United Dominion Realty L.P.
Derivatives and hedging activity
Total amount of Interest expense presented on the Consolidated Statements of Operations	$ 708	$ 161	$ 1,450	$ 351