Consolidation and Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended						9 Months Ended	3 Months Ended
	Mar. 31, 2012	Sep. 30, 2012 States Property Communities	Dec. 31, 2011	Sep. 30, 2012 Development Properties [Member] Communities Property	Sep. 30, 2012 Mid America Multifamily Fund I, LLC Apartments Communities	Sep. 30, 2012 Mid America Multifamily Fund II, LLC Apartments Communities	Sep. 30, 2012 Under Development sqft	Sep. 30, 2012 Additional Paid-in Capital	Sep. 30, 2012 Accumulated Distributions in Excess of Net Income	Sep. 30, 2012 Noncontrolling Interest [Member]	Sep. 30, 2012 Expected Costs [Member]	Sep. 30, 2012 Costs Incurred to Date [Member]
Real Estate Properties [Line Items]
Number of units under development community		1,220
Number of owned or owned interests of apartment communities		167		3	2	4	4
Number of apartments included in a community		49,723		632	626	1,156
Capital improvements in progress		$ 61,801,000	$ 53,790,000								$ 143,900,000	$ 108,800,000
Number of Development Properties		4
Number of states in which apartment units are located		13
Square Footage of Real Estate Property							103,000
Priorperioderroradjustment	$ 655,000							$ 27,000,000	$ 24,900,000	$ 2,100,000