Real Estate Owned (Details Textual) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2013 Communities States Apartment_Homes	Jun. 30, 2013 Communities States Apartment_Homes	Jun. 30, 2012	Jun. 30, 2013 Communities States Apartment_Homes	Jun. 30, 2012	Jun. 30, 2013 Unconsolidated Joint Venture Vitruvian Park [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 Hurricane Sandy [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 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] New York Properties [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] New York Properties [Member]	Dec. 31, 2012 United Dominion Reality L.P. [Member] New York Properties [Member] Apartment_Homes Communities	Jun. 30, 2013 United Dominion Reality L.P. [Member] Hurricane Sandy [Member]	Dec. 31, 2012 United Dominion Reality L.P. [Member] Hurricane Sandy [Member]	Jun. 30, 2013 United Dominion Reality L.P. [Member] Hurricane Sandy [Member]	Dec. 31, 2012 United Dominion Reality L.P. [Member] Hurricane Sandy [Member]	Jun. 30, 2013 Operating Community [Member] Unconsolidated Joint Venture Vitruvian Park [Member] Communities	Jun. 30, 2013 Operating Community [Member] Unconsolidated Joint Venture Vitruvian Park [Member]	Jun. 30, 2013 Operating Community [Member] Unconsolidated Joint Venture Four Texas [Member] Communities	Jun. 30, 2013 Development Community [Member] Unconsolidated Joint Venture Vitruvian Park [Member] Communities	Jun. 30, 2013 Development Community [Member] Unconsolidated Joint Venture Vitruvian Park [Member]	Jun. 30, 2013 Land [Member] Unconsolidated Joint Venture Vitruvian Park [Member] acre Land_Parcels
Real Estate Owned (Textual) [Abstract]
Number of owned and consolidated community by the Company	141	141		141							70		70
Number of states in which there are owned and consolidated communities	10	10		10							9		9
Number of apartment homes owned and consolidated by the Company	41,153	41,153		41,153							21,660		21,660
Percentage of interest sold	50.00%
Number of partnerships of sold interests						5
Proceeds from the sale of interests in partnerships	$ 141,300,000
Transaction costs of selling interest in partnerships	936,000
Joint Venture and Partnership Number of Operating Communities Owned																						2	2	8	1	1	6
Joint Venture and Partnership Number of Apartment Homes in Operating Communities	739	739		739
Number of apartments of development community	391	391		391
Number of developable acres																											28.4
Proceeds from the sale of interests in partnerships	436,000
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				10,400,000		1,423,000	1,305,000	2,809,000	2,623,000					7,000,000
Total Estimated Insurance Recovery										$ 14,500,000											$ 10,800,000