Subsequent Events - Additional Information (Detail) $ in Millions		6 Months Ended
	Jul. 01, 2015 USD ($) apartmentunits Communities	Jun. 30, 2015 apartmentunits Communities	Jul. 30, 2015 apartmentunits	Jul. 28, 2015 apartmentunits
Subsequent Event [Line Items]
Number Of Properties Sold | Communities		1
Number of Units in Real Estate Property		79,977
Subsequent Event [Member]
Subsequent Event [Line Items]
Number Of Properties Sold | Communities	3
Number of Units in Real Estate Property	1,602
Gain on sale of depreciable real estate assets excluded from discontinued operations | $	$ 54
Whisperwood [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property	1,008
Colonial Grand at Wilmington [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property	390
Savannah Creek [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property	204
Radius [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property				252
Manor Homes of Prairie Trace [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property			280