Debt (UNITED DOMINION REALTY, L.P.) (Details 1) (USD $) In Thousands, unless otherwise specified	6 Months Ended				6 Months Ended		12 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Fannie Mae [Member]	Jun. 30, 2012 Fannie Mae [Member]	Dec. 31, 2012 Fannie Mae [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Fannie Mae [Member]	Dec. 31, 2012 United Dominion Reality L.P. [Member] Fannie Mae [Member]	Jun. 30, 2013 Fixed Rate Debt [Member]	Jun. 30, 2013 Fixed Rate Debt [Member] Mortgages [Member]	Jun. 30, 2013 Fixed Rate Debt [Member] Line of Credit [Member]	Jun. 30, 2013 Fixed Rate Debt [Member] United Dominion Reality L.P. [Member]	Jun. 30, 2013 Fixed Rate Debt [Member] United Dominion Reality L.P. [Member] Mortgages [Member]	Jun. 30, 2013 Fixed Rate Debt [Member] United Dominion Reality L.P. [Member] Line of Credit [Member]	Jun. 30, 2013 Variable Rate Debt [Member]	Jun. 30, 2013 Variable Rate Debt [Member] Mortgages [Member]	Jun. 30, 2013 Variable Rate Debt [Member] Tax Exempt Notes Payable [Member]	Jun. 30, 2013 Variable Rate Debt [Member] Line of Credit [Member]	Jun. 30, 2013 Variable Rate Debt [Member] United Dominion Reality L.P. [Member]	Jun. 30, 2013 Variable Rate Debt [Member] United Dominion Reality L.P. [Member] Mortgages [Member]	Jun. 30, 2013 Variable Rate Debt [Member] United Dominion Reality L.P. [Member] Tax Exempt Notes Payable [Member]	Jun. 30, 2013 Variable Rate Debt [Member] United Dominion Reality L.P. [Member] Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	4 years 2 months 26 days				5 years 5 months 20 days			4 years 5 months 14 days	3 years 0 months 3 days	5 years 6 months 3 days	4 years 5 months 23 days	3 years 0 months 7 days	5 years 11 months 26 days	7 years 11 months 6 days	3 months	9 years 8 months 8 days	5 years 0 months 7 days	9 years 10 months 24 days	0 days	18 years 8 months 19 days	8 years 2 months 19 days
Borrowings outstanding	$ 839,700	$ 839,693		$ 842,487		$ 521,225	$ 507,825
Weighted average daily borrowings during the period ended		840,437	903,817			521,687	544,793
Maximum daily borrowings during the period ended		$ 841,494	$ 1,054,735			$ 522,343	$ 635,762
Weighted average interest rate during the period ended		4.30%	4.30%				4.30%
Interest rate at the end of the period		4.20%		4.40%			4.40%