Real Estate Owned (UNITED DOMINION REALTY, L.P.) (Details Textual) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended	3 Months Ended	6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2013 Apartment_Homes Communities States	Jun. 30, 2012 Communities	Jun. 30, 2013 Communities Apartment_Homes States	Jun. 30, 2012 Communities	Jun. 30, 2013 United Dominion Reality L.P. [Member] Communities States Apartment_Homes	Jun. 30, 2012 United Dominion Reality L.P. [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Communities States Apartment_Homes	Jun. 30, 2012 United Dominion Reality L.P. [Member]	Jun. 30, 2013 New York Properties [Member]	Jun. 30, 2013 New York Properties [Member]	Dec. 31, 2012 New York Properties [Member] Apartment_Homes	Jun. 30, 2013 New York Properties [Member] United Dominion Reality L.P. [Member]	Jun. 30, 2013 New York Properties [Member] United Dominion Reality L.P. [Member]	Dec. 31, 2012 New York Properties [Member] United Dominion Reality L.P. [Member] Communities Apartment_Homes	Jun. 30, 2013 Hurricane Sandy [Member] United Dominion Reality L.P. [Member]	Dec. 31, 2012 Hurricane Sandy [Member] United Dominion Reality L.P. [Member]	Jun. 30, 2013 Hurricane Sandy [Member] United Dominion Reality L.P. [Member]
Real Estate Owned (Textual) [Abstract]
Number of communities owned (in communities)	141		141		70		70
Number of states operating within (in states)	10		10		9		9
Number of apartments owned (in apartments homes)	41,153		41,153		21,660		21,660
Number of communities acquired apartment homes are within	0	0	0	0
Number of apartment homes acquired	0		0
Development costs excluding direct costs and capitlized interest	$ 3,100,000	$ 2,000,000	$ 6,100,000	$ 4,700,000	$ 678,000	$ 344,000	$ 1,351,000	$ 883,000
Interest capitalized during period	8,200,000	5,100,000	16,600,000	10,000,000	1,400,000	680,000	2,700,000	1,300,000
Number of Communities Owned											3			2
Number of Apartments Owned											1,706			1,001
Impairment of Long-Lived Assets Held-for-use									0	0	9,000,000	0	0		0	7,100,000	0
Other Cost and Expense, Operating	$ 1,807,000	$ 1,434,000	$ 3,450,000	$ 2,817,000	$ 1,423,000	$ 1,305,000	$ 2,809,000	$ 2,623,000			$ 10,400,000					$ 7,000,000