Discontinued Operations (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 Communities	Jun. 30, 2012 Communities	Jun. 30, 2013 Communities	Jun. 30, 2012 Communities	Dec. 31, 2010
Discontinued Operations (Textual) [Abstract]
Communities sold (in communities)	0	15	0	21
Summary of income from discontinued operations
Rental income	$ 0	$ 13,215,000	$ 0	$ 30,316,000
Rental expenses	0	4,637,000	0	10,566,000
Property management fee	0	364,000	0	834,000
Real estate depreciation	0	0	0	6,340,000
Total expenses	0	5,792,000		18,531,000	0
Income before net gain on the sale of property	0	7,423,000		11,785,000	0
Net (loss)/gain on the sale of property		180,856,000		261,381,000
Income from discontinued operations	0	179,429,000	0	264,316,000	0
United Dominion Reality L.P. [Member]
Discontinued Operations (Textual) [Abstract]
Communities sold (in communities)	0	4	0
Communities held for sale (in communities)	0		0
Summary of income from discontinued operations
Rental income	0	3,377,000	0	6,750,000
Rental expenses	0	1,178,000	0	2,247,000
Property management fee	0	93,000	0	186,000
Real estate depreciation	0	0	0	1,205,000
Total expenses	0	1,271,000	0	3,638,000
Income before net gain on the sale of property	0	2,106,000	0	3,112,000
Net (loss)/gain on the sale of property	0	51,266,000	0	51,182,000
Income from discontinued operations	$ 0	$ 53,372,000	$ 0	$ 54,294,000
Discontinued operations, communities sold (in communities)				4
Discontinued operations, apartment homes sold (in apartment homes)		1,314		1,314