Real Estate Disposition Activities (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 community	Jun. 30, 2013	Jun. 30, 2014 community	Jun. 30, 2013
Summary of income from discontinued operations
Number of Apartment Communities Sold			3
Number Of Communities Held For Sale	0		0
Gain on sale of discontinued operations	$ 0	$ 33,682,000	$ 37,869,000	$ 118,173,000
Gain on sale of communities			98,814,000	118,413,000
Avalon Valley [Member]
Summary of income from discontinued operations
Apartment homes			268
Net proceeds			53,325,000
Gain on sale of discontinued operations			37,869,000
Oakwood Philadelphia [Member]
Summary of income from discontinued operations
Apartment homes	80
Net proceeds	28,875,000
Gain on sale of communities	3,268,000
Avalon Danvers [Member]
Summary of income from discontinued operations
Apartment homes	433
Net proceeds	108,500,000
Gain on sale of communities	$ 41,021,000