Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Rental properties:
Land and land improvements	$ 901,942	$ 860,661
Buildings and improvements	3,702,631	3,452,403
Total Rental Properties	4,604,573	4,313,064
Less: accumulated depreciation	(995,311)	(920,026)
Net Real Estate	3,609,262	3,393,038
Real estate for development	55,343	44,280
Co-investments	436,230	383,412
Total Real Estate	4,100,835	3,820,730
Cash and cash equivalents-unrestricted	4,132	12,889
Cash and cash equivalents-restricted	23,678	22,574
Marketable securities	114,166	74,275
Notes and other receivables	50,895	66,369
Prepaid expenses and other assets	26,859	22,682
Deferred charges, net	18,551	17,445
Total assets	4,339,116	4,036,964
Liabilities and Equity
Mortgage notes payable	1,615,645	1,745,858
Unsecured debt	615,000	465,000
Lines of credit	257,102	150,000
Accounts payable and accrued liabilities	62,636	48,324
Construction payable	3,575	6,505
Dividends payable	43,708	39,611
Derivative liabilities	6,022	3,061
Other liabilities	20,724	20,528
Total liabilities	2,624,412	2,478,887
Commitments and contingencies
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 35,070,620 and 33,888,082 shares issued and outstanding	3	3
Additional paid-in capital	2,017,445	1,844,611
Distributions in excess of accumulated earnings	(425,058)	(408,066)
Accumulated other comprehensive loss, net	(72,915)	(72,771)
Total stockholders' equity	1,593,225	1,437,527
Noncontrolling interest	117,130	116,201
Total equity	1,710,355	1,553,728
Total liabilities and equity	$ 4,339,116	$ 4,036,964