Real Estate Disposition Activities (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) community item	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) community land_parcel item home	Jun. 30, 2014 USD ($)	Dec. 31, 2008 USD ($)
Summary of income from discontinued operations
Number of Apartment Communities Sold | community			1
Number of Land Parcels Sold | land_parcel			2
Proceeds from Sale of Real Estate			$ 135,841	$ 186,651
Gain on sale of real estate	$ 9,625	$ 0	9,647	0
Gain on sale of discontinued operations	$ 0	0	0	37,869
Gain on sale of communities			$ 91,456	98,814
Number Of Communities Held For Sale | community	1		1
Impairment of Real Estate	$ 0	$ 0		$ 0
Other Real Estate Sales [Member]
Summary of income from discontinued operations
Proceeds from Sale of Real Estate			$ 23,820
Gain on sale of real estate			$ 9,626
Avalon on Stamford Harbor [Member]
Summary of income from discontinued operations
Apartment homes | home			323
Number of Boat Slips in Marina Communities | item	74		74
Proceeds from Sale of Real Estate			$ 115,500
Gain on sale of communities			70,936
Other Real Estate Sales [Member]
Summary of income from discontinued operations
Impairment of Real Estate					$ 5,933
Avalon Mills [Member]
Summary of income from discontinued operations
Impairment of Real Estate			$ 800