SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Expenses
Other expenses as a percentage of total purchase price of apartment communities acquired	0.90%	0.64%	0.85%
Federal Income Taxes
Minimum percentage of annual distribution of REIT taxable income for federal or state income tax exemption	90.00%
Minimum percentage of REIT taxable income distributed	100.00%	100.00%	100.00%
Difference between tax basis of assets and reported amount	$ 483,031	$ 420,930
Net income	163,622	47,664	26,318
Net income attributable to noncontrolling interest	(28,320)	(9,808)	(6,237)
Net loss of taxable REIT Subsidiary included in net income	5	4	54
Net loss of taxable VIE, including impairment of real property			821
Net income from REIT operations	135,307	37,860	20,956
Book to tax differences:
Book depreciation and amortization	139,067	114,138	96,153
Tax depreciation and amortization	(143,893)	(117,822)	(96,158)
Gains/losses from capital transactions	(62,507)	(22)	(86)
Carrying value of mortgages	(784)	(575)	(322)
Equity compensation	(857)	(3,928)	(1,770)
Amortization of debt discount		1,409	1,586
Property acquisition costs	2,210	2,551	2,188
Other, net	(1,934)	1,912	1,609
Adjusted taxable income subject to 90% REIT dividend requirement	66,609	35,523	24,156
Minimum percentage by which the distributions exceed the taxable income before capital gains	100.00%
Deferred tax assets	13,168	13,185
Deferred tax asset reserve	13,168	13,185
Maximum
Revenue Recognition
Lease term	1 year
Continuing operations
Advertising
Advertising expenses	5,304	4,665	4,417
Discontinued operations
Advertising
Advertising expenses	$ 151	$ 191	$ 189