Discontinued Operations (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 Communities	Dec. 31, 2013 Communities	Dec. 31, 2012 Apartment_Homes Communities
Document Period End Date									Dec. 31, 2014
Gain (Loss) on Disposition of Property Plant Equipment									$ 138,600,000
Discontinued Operations (Textual) [Abstract]
Discontinued operations, number of communities sold									1	2	21
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax									75,000	41,919,000	260,404,000
Proceeds from Sale of Property, Plant, and Equipment									328,400,000	81,100,000	609,400,000
Number of communities sold									9
Number of apartment homes sold									2,500	914	6,507
Impairment loss, net of tax									0	1,470,000	0
Summary of income from discontinued operations
Rental income									147,000	9,152,000	39,543,000
Rental expenses									225,000	3,511,000	14,106,000
Property management fee									4,000	252,000	1,087,000
Real estate depreciation									0	1,958,000	8,475,000
Interest									21,000	(62,000)	821,000
Income before net gain on the sale of property									(103,000)	3,493,000	15,054,000
Impairment of Long-Lived Assets to be Disposed of									0	(2,355,000)	0
Income tax expense									38,000	885,000	(8,850,000)
Income/(loss) from discontinued operations, net of tax	0	79,000	18,000	(87,000)	41,376,000	884,000	829,000	853,000	10,000	43,942,000	266,608,000
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									10,000	42,364,000	256,533,000
Land
Gain (Loss) on Disposition of Property Plant Equipment									1,100,000
Operating Community [Member]
Gain (Loss) on Disposition of Property Plant Equipment									$ 142,500,000
Discontinued Operations (Textual) [Abstract]
Number of communities sold									1