CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Land and Land Improvements	$ 3,524,350	$ 3,432,769
Real estate:
Buildings and improvements	12,634,057	12,258,009
Furniture, fixtures and equipment	429,308	402,940
Total Capitalized Cost	16,587,715	16,093,718
Less accumulated depreciation	(3,092,205)	(2,874,578)
Net operating real estate	13,495,510	13,219,140
Construction in progress, including land	1,536,368	1,417,246
Land held for development	487,205	180,516
Operating real estate assets held for sale, net	61,939	118,838
Real Estate Investments, Net	15,581,022	14,935,740
Cash and cash equivalents	65,126	509,460
Cash in escrow	103,679	95,625
Resident security deposits	31,290	29,617
Investments in unconsolidated real estate entities	264,616	298,315
Deferred financing costs, net	40,108	39,728
Deferred development costs	28,103	67,029
Prepaid expenses and other assets	206,532	201,209
Total assets	16,320,476	16,176,723
LIABILITIES AND EQUITY
Unsecured notes, net	3,567,831	2,993,265
Variable rate unsecured credit facility	0	0
Mortgage notes payable	2,919,299	3,532,587
Dividends payable	166,113	153,207
Payables for construction	109,158	101,946
Accrued expenses and other liabilities	242,133	244,549
Accrued interest payable	40,809	41,318
Resident security deposits	53,403	49,189
Liabilities related to real estate assets held for sale	657	1,492
Total liabilities	7,099,403	7,117,553
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	10,588	12,765
Equity:
Preferred stock, $0.01 par value; $25 liquidation preference; 50,000,000 shares authorized at June 30, 2015 and December 31, 2014; zero shares issued and outstanding at June 30, 2015 and December 31, 2014	0	0
Common stock, $0.01 par value; 280,000,000 shares authorized at June 30, 2015 and December 31, 2014; 132,888,167 and 132,050,382 shares issued and outstanding at June 30, 2015 and December 31, 2014, respectively	1,329	1,320
Additional paid-in capital	9,466,120	9,354,685
Accumulated earnings less dividends	(217,441)	(267,085)
Accumulated other comprehensive loss	(39,523)	(42,515)
Total equity	9,210,485	9,046,405
Total liabilities and equity	$ 16,320,476	$ 16,176,723