Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Rental properties:
Land and land improvements	$ 823,629	$ 802,325
Buildings and improvements	3,259,095	3,265,014
Total Rental Properties	4,082,724	4,067,339
Less accumulated depreciation	(845,566)	(878,331)
Net Real Estate	3,237,158	3,189,008
Real estate under development	191,620	217,531
Co-investments	197,364	107,840
Total Real Estate	3,626,142	3,514,379
Cash and cash equivalents-unrestricted	8,809	13,753
Cash and cash equivalents-restricted	24,038	21,941
Marketable securities	75,673	92,310
Notes and other receivables	49,956	49,444
Prepaid expenses and other assets	25,444	25,188
Deferred charges, net	15,793	15,872
Total assets	3,825,855	3,732,887
Liabilities and Equity
Mortgage notes payable	1,779,461	1,832,745
Lines of credit	210,000	426,000
Unsecured bonds	265,000	0
Accounts payable and accrued liabilities	49,577	44,750
Construction payable	11,064	9,023
Dividends payable	37,975	36,405
Derivative liabilities	1,506	5,633
Other liabilities	20,171	18,968
Total liabilities	2,374,754	2,373,524
Commitments and contingencies
Cumulative convertible preferred stock; $.0001 par value:
4.875% Series G - 5,980,000 issued and 178,249 outstanding	4,349	4,349
Stockholders' equity and noncontrolling interest:
Common stock, $.0001 par value, 649,702,178 shares authorized 32,724,235 and 31,324,808 shares issued and outstanding	3	3
Additional paid-in capital	1,687,691	1,515,468
Distributions in excess of accumulated earnings	(359,662)	(313,308)
Accumulated other comprehensive (loss) income	(74,918)	(77,217)
Total stockholders' equity	1,326,864	1,149,946
Noncontrolling interest	119,888	205,068
Total stockholders' equity and noncontrolling interest	1,446,752	1,355,014
Total liabilities and equity	3,825,855	3,732,887
7.125% Series H Cumulative Redeemable Preferred Stock [Member]
Stockholders' equity and noncontrolling interest:
Cumulative redeemable preferred stock, liquidation value	73,750	0
7.8125% Series F Cumulative Redeemable Preferred Stock [Member]
Stockholders' equity and noncontrolling interest:
Cumulative redeemable preferred stock, liquidation value	$ 0	$ 25,000