REAL ESTATE OWNED (UNITED DOMINION REALTY, L.P.) - Acquisitions and Dispositions (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) community item state	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) community item state	Sep. 30, 2019 USD ($)
Real Estate Owned Disclosure
Number of communities owned (in communities) | community	148		148
Number of states in which there are owned and consolidated communities | state	13		13
Development costs excluding direct costs and capitalized interest	$ 1.6	$ 1.9	$ 10.3	$ 6.9
Number of apartments owned (in apartments homes) | item	47,488		47,488
Interest capitalized during period	$ 1.8	1.4	$ 4.9	3.8
United Dominion Realty L.P.
Real Estate Owned Disclosure
Number of communities owned (in communities) | community	52		52
Number of states in which there are owned and consolidated communities | state	9		9
Development costs excluding direct costs and capitalized interest	$ 0.2	0.3	$ 0.8	0.6
Number of apartments owned (in apartments homes) | item	16,434		16,434
Interest capitalized during period			$ 0.1	$ 0.1
United Dominion Realty L.P. | Maximum
Real Estate Owned Disclosure
Interest capitalized during period	$ 0.1	$ 0.1