Condensed Consolidated Balance Sheets (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Assets
Land	$ 766,302	$ 760,397
Buildings and improvements	4,758,397	4,680,361
Real estate assets, at cost, total	5,524,699	5,440,758
Accumulated depreciation	(1,421,867)	(1,292,924)
Net operating real estate assets	4,102,832	4,147,834
Properties under development, including land	274,201	206,919
Investments in joint ventures	37,033	27,632
Total real estate assets	4,414,066	4,382,385
Accounts receivable - affiliates	31,395	31,895
Notes receivable - affiliates		3,194
Other assets, net	87,657	106,175
Cash and cash equivalents	56,099	170,575
Restricted cash	5,357	5,513
Total assets	4,594,574	4,699,737
Liabilities
Unsecured notes payable	1,380,560	1,507,757
Secured notes payable	1,052,544	1,055,997
Accounts payable and accrued expenses	97,613	81,556
Accrued real estate taxes	37,721	22,338
Distributions payable	39,319	35,295
Other liabilities	111,043	141,496
Total liabilities	2,718,800	2,844,439
Commitments and contingencies
Perpetual preferred units	97,925	97,925
Equity
Common shares of beneficial interest; $0.01 par value per share; 100,000 shares authorized; 86,763 and 85,130 issued; 83,874 and 82,386 outstanding at September 30, 2011 and December 31, 2010, respectively	839	824
Additional paid-in capital	2,861,139	2,775,625
Distributions in excess of net income attributable to common shareholders	(700,897)	(595,317)
Treasury shares, at cost (12,516 and 12,766 common shares at September 30, 2011 and December 31, 2010, respectively)	(452,244)	(461,255)
Accumulated other comprehensive income (loss)	201	(33,458)
Total common equity	1,709,038	1,686,419
Noncontrolling interests	68,811	70,954
Total equity	1,777,849	1,757,373
Total liabilities and equity	$ 4,594,574	$ 4,699,737