REAL ESTATE OWNED (UNITED DOMINION REALTY, L.P.) - Acquisitions and Dispositions (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) state item community	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) state item community	Jun. 30, 2019 USD ($)
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	$ 1.8	$ 1.8	$ 8.7	$ 5.0
Number of apartments owned (in apartments homes) | item	47,371		47,371
Interest capitalized during period	$ 1.7	1.2	$ 3.0	2.3
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	$ 0.6	0.3
Number of apartments owned (in apartments homes) | item	16,434		16,434
United Dominion Realty L.P. | Maximum
Real Estate Owned Disclosure
Interest capitalized during period	$ 0.1	$ 0.1	$ 0.1	$ 0.1