Organization and Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Y Apartment Property	Dec. 31, 2011	Dec. 31, 2010
Real Estate Properties [Line Items]
Number of units in real estate property	22,218
Number of communities in apartment units	60
Common stock, shares outstanding	54,470,000	52,988,000
Ownership interest percentage in Operating Partnership	99.70%	99.70%	99.70%
Common units held by persons other than the Company	143,000
Noncontrolling interest, ownership percentage by noncontrolling owners	0.30%
Revenue recognized lease (in years)	1
Operating leases term (in years)	1
Development or construction costs	$ 3,755	$ 2,854	$ 719
Investment maturity period maximum (in months)	Three
Atlanta, Georgia [Member]
Real Estate Properties [Line Items]
Concentration of location for communities, percentage	31.50%
Dallas, Texas [Member]
Real Estate Properties [Line Items]
Concentration of location for communities, percentage	22.60%
Washington, D.C. [Member]
Real Estate Properties [Line Items]
Concentration of location for communities, percentage	13.90%
Tampa, Florida [Member]
Real Estate Properties [Line Items]
Concentration of location for communities, percentage	10.10%
Buildings And Components [Member]
Real Estate Properties [Line Items]
Estimated useful life (in years)	40 years
Other Building And Land Improvements [Member]
Real Estate Properties [Line Items]
Estimated useful life (in years)	20 years
Furniture, Fixtures And Equipment [Member] | Minimum [Member]
Real Estate Properties [Line Items]
Estimated useful life (in years)	5 years
Furniture, Fixtures And Equipment [Member] | Maximum [Member]
Real Estate Properties [Line Items]
Estimated useful life (in years)	10 years
Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Number of units in real estate property	1,471
Number of communities in apartment units	4
Under Development [Member]
Real Estate Properties [Line Items]
Number of units in real estate property	2,046
Number of communities in apartment units	7
For-Sale Condominium Homes [Member]
Real Estate Properties [Line Items]
Number of communities in apartment units	2
Cost Capitalization [Member]
Real Estate Properties [Line Items]
Weighted average borrowing costs, percentage	5.40%	6.00%	6.30%
Residential Leases [Member] | Minimum [Member]
Real Estate Properties [Line Items]
Average remaining lease term	6 months
Residential Leases [Member] | Maximum [Member]
Real Estate Properties [Line Items]
Average remaining lease term	12 months
Retail Leases [Member] | Minimum [Member]
Real Estate Properties [Line Items]
Average remaining lease term	5 years
Retail Leases [Member] | Maximum [Member]
Real Estate Properties [Line Items]
Average remaining lease term	10 years