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		6 Months Ended			6 Months Ended		6 Months Ended		6 Months Ended			6 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Fixed Rate Debt [Member] Communities	Dec. 31, 2012 Fixed Rate Debt [Member]	Jun. 30, 2013 Fixed Rate Debt [Member] Mortgages Notes Payable [Member] Communities	Dec. 31, 2012 Fixed Rate Debt [Member] Mortgages Notes Payable [Member]	Jun. 30, 2013 Fixed Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Dec. 31, 2012 Fixed Rate Debt [Member] Fannie Mae credit facilities [Member]	Jun. 30, 2013 Variable Rate Debt [Member] Communities	Dec. 31, 2012 Variable Rate Debt [Member]	Jun. 30, 2013 Variable Rate Debt [Member] Mortgages Notes Payable [Member] Communities	Dec. 31, 2012 Variable Rate Debt [Member] Mortgages Notes Payable [Member]	Jun. 30, 2013 Variable Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Dec. 31, 2012 Variable Rate Debt [Member] Fannie Mae credit facilities [Member]	Jun. 30, 2013 Variable Rate Debt [Member] Tax Exempt Notes Payable [Member] Communities	Dec. 31, 2012 Variable Rate Debt [Member] Tax Exempt Notes Payable [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Communities	Dec. 31, 2012 United Dominion Reality L.P. [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Fannie Mae credit facilities [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Communities	Dec. 31, 2012 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Mortgages Notes Payable [Member] Communities	Dec. 31, 2012 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Mortgages Notes Payable [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Fixed Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Jun. 30, 2013 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Communities	Dec. 31, 2012 United Dominion Reality L.P. [Member] Variable Rate Debt [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Mortgages Notes Payable [Member] Communities	Dec. 31, 2012 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Mortgages Notes Payable [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Fannie Mae credit facilities [Member] Communities	Jun. 30, 2013 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Tax Exempt Notes Payable [Member] Communities	Dec. 31, 2012 United Dominion Reality L.P. [Member] Variable Rate Debt [Member] Tax Exempt Notes Payable [Member]	Jun. 30, 2013 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]	Jun. 30, 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]	Dec. 31, 2012 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]	Jun. 30, 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]	Dec. 31, 2012 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		$ 1,078,925	$ 1,086,611	$ 450,641	$ 455,533		$ 631,078	$ 306,109	$ 343,524	$ 0	$ 37,415	$ 211,409	$ 211,409	$ 94,700	$ 94,700	$ 939,148	$ 967,239	$ 521,200	$ 770,090	$ 765,637	$ 390,923	$ 394,999		$ 169,058	$ 201,602	$ 0	$ 37,415		$ 27,000	$ 27,000	$ 211,409	$ 379,167	$ 370,638	$ 142,058	$ 137,187
Weighted Average Interest Rate	4.20%	5.17%		5.42%				1.40%		0.00%				0.89%		4.48%			5.07%		5.42%			1.78%
Number of Communities Encumbered (in communities)		30		8		22		9		0		7		2		21			15		5		10	6		0		5	1
Debt, Weighted Average Interest Rate						4.99%																	4.71%					1.92%
Debt Instrument, Interest Rate at Period End												1.63%														0.00%			1.05%