Real Estate Acquisitions and Dispositions - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2015 ft² a apartmentunits Communities Apartments	Oct. 14, 2015 a
Business Acquisitions and Dispositions [Line Items]
Number Of Properties Sold | Communities	1
Number of Units in Real Estate Property | apartmentunits	79,024
Colonial Promenade Craft Farms [Member]
Business Acquisitions and Dispositions [Line Items]
Square Footage of Real Estate Property | ft²	67,735
Area of Land | a	0.23
River's Walk [Member]
Business Acquisitions and Dispositions [Line Items]
Area of Land | a	2.5
Residences at Burlington Creek [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	298
Vistas [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	144
Austin Chase [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	256
Fairways At Hartland [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	240
Fountain Lake [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	113
Westbury Creek [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	120
Woodwinds [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	144
Colony At South Park [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	184
Bradford Pointe [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	192
Anatole [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	208
Oaks [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	100
Post House Jackson [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	150
Woods of Post House [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	122
Post House North [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	145
Bradford Chase [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	148
Sutton Place [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	253
Southland Station [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	304
Huntington Chase [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	200
SkySong [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	325
Retreat at West Creek [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	254
Paddock Park Ocala [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	480
Colonial Grand at Wilmington [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	390
Savannah Creek [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	204
Radius [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	252
Haven at Prairie Trace [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	280
Whisperwood [Member]
Business Acquisitions and Dispositions [Line Items]
Number of Units in Real Estate Property	1,008
Subsequent Event [Member] | Retreat at West Creek [Member]
Business Acquisitions and Dispositions [Line Items]
Area of Land | a		4.4