Consolidation and Basis of Presentation (UNITED DOMINION REALTY, L.P.) (Details)	12 Months Ended
	Dec. 31, 2014 Markets Apartment_Homes	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidation and Basis of Presentation [Line Items]
Number of markets operating within	20
Number of apartments owned	39,851
Operating Partnership outstanding units	183,278,698	183,278,698
OP units outstanding related to limited partner	183,278,698	183,278,698	184,281,254	184,281,254
United Dominion Reality L.P.
Consolidation and Basis of Presentation [Line Items]
Rental revenues percent of General Partner's consolidated rental revenues	52.00%	54.00%	54.00%
Number of markets operating within	17
Number of apartments owned	20,814
OP units outstanding related to general partner	110,883	110,883
Percentage of total outstanding Operating Partnership units represented by General Partnership units outstanding	0.06%
OP units outstanding related to limited partner	183,167,815	183,167,815
UDR, Inc.
Consolidation and Basis of Presentation [Line Items]
OP units outstanding related to limited partner	174,002,342	173,848,891
Percentage of units outstanding owned by limited partners	95.00%	94.90%
Non-affiliated Partners
Consolidation and Basis of Presentation [Line Items]
OP units outstanding related to limited partner	9,165,473	9,318,924
Percentage of units outstanding owned by limited partners	5.00%	5.10%
Class A Limited Partner
Consolidation and Basis of Presentation [Line Items]
OP units outstanding related to limited partner	1,751,671
Class A Limited Partner | United Dominion Reality L.P.
Consolidation and Basis of Presentation [Line Items]
OP units outstanding related to limited partner	1,873,332	1,751,671