Real Estate Disposition Activities (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Summary of income from discontinued operations
Gain on sale of communities	$ 37,869,000	$ 84,491,000
Avalon Valley
Summary of income from discontinued operations
Apartment homes	268
Net proceeds	53,325,000
Gain on sale of communities	37,869,000
Arna Valley View
Summary of income from discontinued operations
Apartment homes	101
Amount received on sale of limited partnership for residual ownership interest	$ 2,195,000