Related Party Transactions (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	3 Months Ended		6 Months Ended				6 Months Ended		3 Months Ended		6 Months Ended				6 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 United Dominion Reality L.P. [Member]	Dec. 31, 2012 United Dominion Reality L.P. [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Taxable REIT Subsidiaries [Member]	Jun. 30, 2012 United Dominion Reality L.P. [Member] Taxable REIT Subsidiaries [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] UDR, Inc. [Member]	Jun. 30, 2012 United Dominion Reality L.P. [Member] UDR, Inc. [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] UDR, Inc. [Member]	Jun. 30, 2012 United Dominion Reality L.P. [Member] UDR, Inc. [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] UDR, Inc. [Member] Bottom Dollar Guaranty [Member]	Dec. 31, 2012 United Dominion Reality L.P. [Member] UDR, Inc. [Member] Bottom Dollar Guaranty [Member]	Jun. 30, 2012 United Dominion Reality L.P. [Member] UDR, Inc. [Member] Guaranty related to community acquisition [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] UDR, Inc. [Member] Guaranty related to community acquisition [Member]	Dec. 31, 2012 United Dominion Reality L.P. [Member] UDR, Inc. [Member] Guaranty related to community acquisition [Member]	Jun. 30, 2013 Bottom Dollar Guaranty [Member] Fixed Rate Debt [Member] United Dominion Reality L.P. [Member]
Related Party Transaction [Line Items]
Net receivable balances from General Partner					$ 65,449,000	$ (11,056,000)	$ (65,449,000)	$ 11,056,000
General and administrative expenses allocated to the Operating Partnership by UDR									5,600,000	7,100,000	10,900,000	14,600,000
Related Party Transaction, Management Fee Percentage					2.75%		2.75%
Related party management fees	3,000,000	2,800,000	6,000,000	5,500,000
Related party guaranty note payable interest rate													0.932%	0.93%		5.337%
Debt Instrument, Maturity Date Range, End																		Aug. 31, 2021
Notes payable due to General Partner					$ 88,696,000	$ 88,696,000							$ 83,200,000	$ 83,200,000		$ 5,500,000	$ 5,500,000
Number of OP Units issued as consideration for acquisition guaranteed by related party note payable (in shares)															1,802,239