Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Rental properties:
Land and land improvements	$ 934,282	$ 860,661
Buildings and improvements	3,823,382	3,452,403
Total Rental Properties	4,757,664	4,313,064
Less: accumulated depreciation	(1,037,663)	(920,026)
Net Real Estate	3,720,001	3,393,038
Real estate under development	60,020	44,280
Co-investments	477,967	383,412
Total Real Estate	4,257,988	3,820,730
Cash and cash equivalents-unrestricted	1,943	12,889
Cash and cash equivalents-restricted	24,934	22,574
Marketable securities	141,573	74,275
Notes and other receivables	50,316	66,369
Prepaid expenses and other assets	36,517	22,682
Deferred charges, net	21,401	17,445
Total assets	4,534,672	4,036,964
Liabilities and Equity
Mortgage notes payable	1,571,821	1,745,858
Unsecured debt	962,008	465,000
Lines of credit	61,872	150,000
Accounts payable and accrued liabilities	76,828	48,324
Construction payable	4,266	6,505
Dividends payable	44,377	39,611
Derivative liabilities	7,174	3,061
Other liabilities	20,886	20,528
Total liabilities	2,749,232	2,478,887
Cumulative convertible Series G preferred stock	4,349	4,349
Equity
Cumulative redeemable Series H preferred stock at liquidation value	73,750	73,750
Common stock, $.0001 par value, 656,020,000 shares authorized 35,714,182 and 33,888,082 shares issued and outstanding	3	3
Additional paid-in capital	2,116,531	1,844,611
Distributions in excess of accumulated earnings	(448,142)	(408,066)
Accumulated other comprehensive loss, net	(76,449)	(72,771)
Total stockholders' equity	1,665,693	1,437,527
Noncontrolling interest	115,398	116,201
Total equity	1,781,091	1,553,728
Total liabilities and equity	$ 4,534,672	$ 4,036,964