Related Party Transactions (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2014
Related Party Transaction [Line Items]
Related party management fees	$ 12,700,000	$ 12,300,000	$ 11,900,000
Limited Partners' Capital Account, Units Redeemed		1,002,556
United Dominion Reality L.P.
Related Party Transaction [Line Items]
Net receivable balances from General Partner	(13,624,000)	9,916,000
Related party management fee percentage	2.75%
Notes payable due to General Partner	88,696,000	88,696,000
OP Units issued for real estate	77,041,000		0
United Dominion Reality L.P. | Taxable REIT Subsidiaries
Related Party Transaction [Line Items]
Net receivable balances from General Partner	13,624,000	(9,916,000)
Related party management fee percentage	2.75%
United Dominion Reality L.P. | UDR, Inc.
Related Party Transaction [Line Items]
General and administrative expenses allocated to the Operating Partnership by UDR	27,400,000	23,500,000	25,200,000
United Dominion Reality L.P. | UDR, Inc. | Bottom Dollar guaranty
Related Party Transaction [Line Items]
Related party guaranty note payable interest rate	5.18%	5.18%		5.18%
Notes payable due to General Partner	83,200,000	83,300,000
United Dominion Reality L.P. | UDR, Inc. | Guaranty related to community acquisition
Related Party Transaction [Line Items]
Related party guaranty note payable interest rate	5.337%
Notes payable due to General Partner	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
Receivable Due From General Partner [Member] | United Dominion Reality L.P.
Related Party Transaction [Line Items]
OP Units issued for real estate	$ 53,712,000