Discontinued Operations (Details) (USD $)	3 Months Ended							12 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
REVENUES
Rental income								$ 69,619,000	$ 202,128,000	$ 388,480,000
Total revenues								69,619,000	202,128,000	388,480,000
EXPENSES
Property and maintenance								19,575,000	76,727,000	143,158,000
Real estate taxes and insurance								6,055,000	17,061,000	34,148,000
Disposal Group Including Discontinued Operations Property Management								211,000	266,000	230,000
Depreciation								20,910,000	51,037,000	91,934,000
General and administrative								77,000	54,000	42,000
Total expenses								46,828,000	145,145,000	269,512,000
Discontinued operating income								22,791,000	56,983,000	118,968,000
Interest and other income								155,000	196,000	848,000
Other expenses								(120,000)	(265,000)	(136,000)
Interest:
Expense incurred, net								(1,381,000)	(5,163,000)	(17,628,000)
Amortization of deferred financing costs								(65,000)	(1,080,000)	(830,000)
Income and other tax (expense) benefit								(9,000)	243,000	(87,000)
Discontinued operations								21,371,000	50,914,000	101,135,000
Net gain on sales of discontinued operations								548,278,000	826,489,000	297,956,000
Discontinued operations, net	107,890,000	78,102,000	139,513,000	74,895,000	84,703,000	571,417,000	146,388,000	569,649,000	877,403,000	399,091,000
Disposal Group, Including Discontinued Operation, Property, Plant, and Equipment, Net				516,000,000					516,000,000
Disposal Group Including Discontinued Operation Mortgage Notes Payable				$ 87,400,000					$ 87,400,000