Debt (UNITED DOMINION REALTY, L.P.) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Fixed Rate Debt [Member] Communities	Dec. 31, 2013 Fixed Rate Debt [Member]	Sep. 30, 2014 Fixed Rate Debt [Member] Mortgages Notes Payable [Member] Communities	Dec. 31, 2013 Fixed Rate Debt [Member] Mortgages Notes Payable [Member]	Sep. 30, 2014 Fixed Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Dec. 31, 2013 Fixed Rate Debt [Member] Fannie Mae credit facilities [Member]	Sep. 30, 2014 Variable Rate Debt [Member] Communities	Dec. 31, 2013 Variable Rate Debt [Member]	Sep. 30, 2014 Variable Rate Debt [Member] Mortgages Notes Payable [Member] Communities	Dec. 31, 2013 Variable Rate Debt [Member] Mortgages Notes Payable [Member]	Sep. 30, 2014 Variable Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Dec. 31, 2013 Variable Rate Debt [Member] Fannie Mae credit facilities [Member]	Sep. 30, 2014 Variable Rate Debt [Member] Tax Exempt Notes Payable [Member] Communities	Dec. 31, 2013 Variable Rate Debt [Member] Tax Exempt Notes Payable [Member]	Sep. 30, 2014 United Dominion Reality L.P. [Member] Communities	Dec. 31, 2013 United Dominion Reality L.P. [Member]	Sep. 30, 2014 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Communities	Dec. 31, 2013 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member]	Sep. 30, 2014 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Mortgages Notes Payable [Member] Communities	Dec. 31, 2013 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Mortgages Notes Payable [Member]	Sep. 30, 2014 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Sep. 30, 2014 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Communities	Dec. 31, 2013 United Dominion Reality L.P. [Member] Variable Rate Debt [Member]	Sep. 30, 2014 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Sep. 30, 2014 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Tax Exempt Notes Payable [Member] Communities	Dec. 31, 2013 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Tax Exempt Notes Payable [Member]	Sep. 30, 2014 Line of Credit [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] Variable Rate Debt [Member] Fannie Mae credit facilities [Member]	Sep. 30, 2014 Line of Credit [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Fannie Mae credit facilities [Member]	Dec. 31, 2013 Line of Credit [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Fannie Mae credit facilities [Member]	Sep. 30, 2014 Line of Credit [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Fannie Mae credit facilities [Member]	Dec. 31, 2013 Line of Credit [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding		$ 1,061,926	$ 1,072,373	$ 438,172	$ 445,706		$ 626,667	$ 337,446	$ 369,704	$ 31,337	$ 63,595	$ 211,409	$ 211,409	$ 94,700	$ 94,700	$ 928,273	$ 934,865	$ 759,215	$ 765,806	$ 380,506	$ 386,803		$ 169,058	$ 169,059		$ 27,000	$ 27,000	$ 211,409	$ 378,709	$ 379,003	$ 142,058	$ 142,059
Weighted average interest rate	3.98%	5.19%		5.47%				1.39%		1.94%				0.77%		4.47%		5.09%		5.46%			1.70%
Number of Communities Encumbered (in communities)		30		8		22		10		1		7		2		21		15		5		10	6		5	1
Debt, Weighted Average Interest Rate						4.99%																4.71%			1.88%
Debt Instrument, Interest Rate at Period End												1.58%														0.74%