Discontinued Operations - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2014 Communities Property	Dec. 31, 2013 Communities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number Of Properties Sold	1	9
Number of owned or owned interests of apartment communities	265
Number of Units in Real Estate Property	81,137
Willow Creek
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Units in Real Estate Property	285
Colonial Promenade Nord du Lac
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Footage of Real Estate Property	195,536
Held For Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of owned or owned interests of apartment communities	1