CONDENSED CONSOLIDATED BALANCE SHEETS (USD $)	Sep. 30, 2013	Dec. 31, 2012
Real estate:
Land	$ 3,302,403,000	$ 1,424,797,000
Buildings and improvements	11,116,909,000	6,934,099,000
Furniture, fixtures and equipment	333,638,000	251,537,000
Total Capitalized Cost	14,752,950,000	8,610,433,000
Less accumulated depreciation	(2,445,294,000)	(1,988,764,000)
Net operating real estate	12,307,656,000	6,621,669,000
Construction in progress, including land	1,418,836,000	802,857,000
Land held for development	282,285,000	316,037,000
Operating real estate assets held for sale, net	275,874,000	274,556,000
Total real estate, net	14,284,651,000	8,015,119,000
Cash and cash equivalents	112,910,000	2,733,618,000
Cash in escrow	98,429,000	49,950,000
Resident security deposits	27,868,000	24,748,000
Investments in unconsolidated real estate entities	347,386,000	129,352,000
Deferred financing costs, net	39,085,000	38,700,000
Deferred development costs	33,799,000	24,665,000
Prepaid expenses and other assets	200,979,000	143,926,000
Total assets	15,145,107,000	11,160,078,000
LIABILITIES AND EQUITY
Unsecured notes, net	2,245,191,000	1,945,798,000
Mortgage notes payable	3,852,441,000	1,905,235,000
Dividends payable	138,459,000	110,966,000
Payables for construction	84,027,000	52,903,000
Accrued expenses and other liabilities	254,144,000	217,259,000
Accrued interest payable	23,965,000	33,056,000
Resident security deposits	47,020,000	37,691,000
Liabilities related to real estate assets held for sale	8,275,000	9,350,000
Total liabilities	6,653,522,000	4,312,258,000
Redeemable noncontrolling interests	18,255,000	7,027,000
Equity:
Preferred stock, $0.01 par value; $25 liquidation preference; 50,000,000 shares authorized at both September 30, 2013 and December 31, 2012; zero shares issued and outstanding at September 30, 2013 and December 31, 2012, respectively
Common stock, $0.01 par value; 280,000,000 shares authorized at September 30, 2013 and 140,000,000 shares authorized at December 31, 2012; 129,402,556 and 114,403,472 shares issued and outstanding at September 30, 2013 and December 31, 2012, respectively	1,294,000	1,144,000
Additional paid-in capital	8,976,780,000	7,086,407,000
Accumulated earnings less dividends	(458,229,000)	(142,329,000)
Accumulated other comprehensive loss	(50,094,000)	(108,007,000)
Total equity	8,469,751,000	6,837,215,000
Noncontrolling interest	3,579,000	3,578,000
Total equity	8,473,330,000	6,840,793,000
Total liabilities and equity	$ 15,145,107,000	$ 11,160,078,000