Real Estate Owned (UNITED DOMINION REALTY, L.P.) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Summary of carrying amounts for real estate owned (at cost)
Land	$ 1,265,049	$ 1,907,169
Depreciable property - held and used:
Building and improvements	6,054,933	5,384,971
Furniture, fixtures and equipment	262,999	272,640
Under development:
Under development	432,461	489,795
Real estate owned	8,016,688	8,055,828
Accumulated depreciation	(2,071,649)	(1,924,682)
Total real estate owned, net of accumulated depreciation	5,945,039	6,131,146
Land [Member]
Under development:
Under development	112,091	151,154
Construction in progress [Member]
Under development:
Under development	321,616	339,894
United Dominion Reality L.P. [Member]
Summary of carrying amounts for real estate owned (at cost)
Land	1,012,488	1,006,724
Depreciable property - held and used:
Building and improvements	3,007,677	2,970,510
Furniture, fixtures and equipment	122,899	118,294
Under development:
Under development	118,449	86,260
Real estate owned	4,262,645	4,182,920
Accumulated depreciation	(1,187,753)	(1,097,133)
Total real estate owned, net of accumulated depreciation	3,074,892	3,085,787
United Dominion Reality L.P. [Member] | Land [Member]
Under development:
Under development	25,833	25,833
United Dominion Reality L.P. [Member] | Construction in progress [Member]
Under development:
Under development	$ 93,748	$ 61,559