REAL ESTATE OWNED (UNITED DOMINION REALTY, L.P.) - Acquisitions and Dispositions (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) community state item	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) community state item	Jun. 30, 2018 USD ($)
Real Estate Owned Disclosure
Number of communities owned (in communities) | community	135		135
Number of states in which there are owned and consolidated communities | state	12		12
Development costs excluding direct costs and capitalized interest	$ 1.8	$ 1.6	$ 5.0	$ 5.0
Number of apartments owned (in apartments homes) | item	42,292		42,292
Interest capitalized during period	$ 1.2	3.6	$ 2.3	8.2
United Dominion Reality 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			$ 0.3
Number of apartments owned (in apartments homes) | item	16,434		16,434
United Dominion Reality L.P. | Maximum
Real Estate Owned Disclosure
Development costs excluding direct costs and capitalized interest	$ 0.3	0.1		0.1
Interest capitalized during period	$ 0.1	$ 0.1	$ 0.1	$ 0.1