CONDENSED CONSOLIDATED BALANCE SHEETS (USD $)	Jun. 30, 2014	Dec. 31, 2013
Real estate:
Land	$ 3,417,425,000	$ 3,299,686,000
Buildings and improvements	11,739,025,000	11,108,241,000
Furniture, fixtures and equipment	374,802,000	341,423,000
Total Capitalized Cost	15,531,252,000	14,749,350,000
Less accumulated depreciation	(2,695,462,000)	(2,482,409,000)
Net operating real estate	12,835,790,000	12,266,941,000
Construction in progress, including land	1,478,306,000	1,582,986,000
Land held for development	195,673,000	300,364,000
Operating real estate assets held for sale, net	0	133,918,000
Total real estate, net	14,509,769,000	14,284,209,000
Cash and cash equivalents	425,741,000	281,355,000
Cash in escrow	93,385,000	98,564,000
Resident security deposits	29,538,000	26,672,000
Investments in unconsolidated real estate entities	318,640,000	367,866,000
Deferred financing costs, net	40,928,000	40,677,000
Deferred development costs	34,810,000	31,592,000
Prepaid expenses and other assets	205,140,000	197,208,000
Total assets	15,657,951,000	15,328,143,000
LIABILITIES AND EQUITY
Unsecured notes, net	2,695,112,000	2,594,709,000
Variable rate unsecured credit facility	0	0
Mortgage notes payable	3,559,762,000	3,539,642,000
Dividends payable	152,113,000	138,476,000
Payables for construction	96,021,000	94,632,000
Accrued expenses and other liabilities	227,917,000	242,418,000
Accrued interest payable	40,468,000	43,175,000
Resident security deposits	48,942,000	44,872,000
Liabilities related to real estate assets held for sale	0	13,172,000
Total liabilities	6,820,335,000	6,711,096,000
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	16,084,000	17,320,000
Equity:
Preferred stock, $0.01 par value; $25 liquidation preference; 50,000,000 shares authorized at both June 30, 2014 and December 31, 2013; zero shares issued and outstanding at both June 30, 2014 and December 31, 2013	0	0
Common stock, $0.01 par value; 280,000,000 shares authorized at both June 30, 2014 and December 31, 2013; 131,129,795 and 129,416,695 shares issued and outstanding at June 30, 2014 and December 31, 2013, respectively	1,311,000	1,294,000
Additional paid-in capital	9,213,433,000	8,988,723,000
Accumulated earnings less dividends	(347,592,000)	(345,254,000)
Accumulated other comprehensive loss	(45,620,000)	(48,631,000)
Total stockholders' equity	8,821,532,000	8,596,132,000
Noncontrolling interests	0	3,595,000
Total equity	8,821,532,000	8,599,727,000
Total liabilities and equity	$ 15,657,951,000	$ 15,328,143,000