Consolidation and Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Real Estate Properties [Line Items]
General Partners' Capital Account, Units Outstanding	75,242,266	42,744,978		75,242,266	42,744,978
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest				94.70%	96.20%
Conversion of Stock, Shares Converted				0.36
Number of Wholly Owned Real Estate Properties	265			265
Number of apartments included in a community	81,137			81,137
Number of states in which apartment units are located	14			14
Number of owned or owned interests of apartment communities	265			265
Prior period error adjustment	$ 2,300,000
Quantifying Misstatement in Prior Period Financial Statements, Net Income Available for Common Shareholders						800,000
Quantifying Misstatement in Current Year Financial Statements, Amount						$ 0.01
Percentage Of Ownership Interests	100.00%			100.00%
Minimum [Member]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests	95.00%			95.00%
Maximum [Member]
Real Estate Properties [Line Items]
Percentage Of Ownership Interests	100.00%			100.00%
Parent Company [Member]
Real Estate Properties [Line Items]
Development and capital improvements in progress	59,161,000			59,161,000		166,048,000
Exercise of stock options	2,400,000			11,916,000	0	9,500,000
Gain on sale of depreciable real estate assets excluded from discontinued operations	36,032,000	0	6,200,000	42,254,000	0
Gain on sale of non-depreciable real estate assets	0	0	500,000	535,000	0
Development Properties [Member]
Real Estate Properties [Line Items]
Number of apartments included in a community	0			0
Number of owned or owned interests of apartment communities	2			2
Number of units under development community	514			514
Development Properties [Member] | Expected Costs [Member]
Real Estate Properties [Line Items]
Development and capital improvements in progress	72,900,000			72,900,000
Development Properties [Member] | Costs Incurred to Date [Member]
Real Estate Properties [Line Items]
Development and capital improvements in progress	$ 49,200,000			$ 49,200,000
Retail
Real Estate Properties [Line Items]
Square Footage of Real Estate Property	100,000			100,000
Number of owned or owned interests of apartment communities	4			4
Commercial Real Estate [Member]
Real Estate Properties [Line Items]
Square Footage of Real Estate Property	287,000			287,000
Number of owned or owned interests of apartment communities	3			3
Partially Owned Properties [Member]
Real Estate Properties [Line Items]
Square Footage of Real Estate Property	30,000			30,000
Number of owned or owned interests of apartment communities	1			1
McKinney
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage	25.00%			25.00%
Real Estate Acquired, Number of Units				0
Land Title Building
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage	33.30%			33.30%
Square Footage of Real Estate Property	29,971			29,971