Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 Communities	Jun. 30, 2012 Apartment_Homes Communities	Jun. 30, 2013 Communities	Jun. 30, 2012 Apartment_Homes Communities	Dec. 31, 2010
Discontinued Operations (Textual) [Abstract]
Communities sold (in communities)	0	15	0	21
Apartment homes sold (in apartment homes)		4,931		6,507
Summary of income from discontinued operations
Rental income	$ 0	$ 13,215	$ 0	$ 30,316
Rental expenses	0	4,637	0	10,566
Property management fee	0	364	0	834
Real estate depreciation	0	0	0	6,340
Disposal Group, Including Discontinued Operation, Non Property Expense	0	791	0	791
Total expenses	0	5,792		18,531	0
Income before net gain on the sale of property	0	7,423		11,785	0
Gain on the sale of depreciable property		180,856		261,381
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	0	172,006	0	252,531
Income from discontinued operations	0	179,429	0	264,316	0
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 0	$ 172,643	$ 0	$ 254,179