CAPITAL STRUCTURE (UNITED DOMINION REALTY, L.P.) - Units Rollforward (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capital structure
Balance	183,350,924	183,278,698	183,278,698
Vesting of LTIP Units	285,619	72,226
Balance	183,636,543	183,350,924	183,278,698
Class A Limited Partner
Capital structure
Balance	1,751,671
Balance	1,751,671	1,751,671
Class A Limited Partner | UDR, Inc.
Capital structure
Balance	121,661	121,661	121,661
Balance	121,661	121,661	121,661
Class A Limited Partner | Non-affiliated Partners
Capital structure
Balance	1,751,671
Balance	1,751,671	1,751,671
Non-affiliated Partners
Capital structure
Balance	174,005,144	173,997,540	173,992,855
OP redemptions for UDR stock	11,011	7,604	4,685
Balance	174,016,155	174,005,144	173,997,540
Non-affiliated Partners | Class A Limited Partner
Capital structure
Balance	1,751,671	1,751,671	1,751,671
Balance	1,751,671	1,751,671	1,751,671
Limited Partner | UDR, Inc.
Capital structure
Balance	7,361,565	7,296,943	7,301,628
Vesting of LTIP Units	285,619	72,226
OP redemptions for UDR stock	(11,011)	(7,604)	(4,685)
Balance	7,636,173	7,361,565	7,296,943
General Partner | UDR, Inc.
Capital structure
Balance	110,883	110,883	110,883
Balance	110,883	110,883	110,883