Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Real estate assets:
Land	$ 905,310	$ 905,339
Buildings and improvements	7,215,147	7,228,293
Real estate investment property, at cost	8,120,457	8,133,632
Accumulated depreciation	(2,026,560)	(1,972,031)
Real estate investment property, net, before developments in progress	6,093,897	6,161,601
Held-for-sale	0	29,425
Developments in progress	164,948	137,956
Net investment in real estate assets	6,258,845	6,328,982
Cash and cash equivalents	66,580	78,248
Receivables:
Tenant, net of allowance for doubtful accounts of $2,054 and $1,977 in 2013 and 2012, respectively	76,331	78,963
Other, net of allowance for doubtful accounts of $1,283 and $1,270 in 2013 and 2012, respectively	15,571	8,467
Mortgage and other notes receivable	22,337	25,967
Investments in unconsolidated affiliates	275,349	259,810
Intangible lease assets and other assets	275,064	309,299
Total assets	6,990,077	7,089,736
LIABILITIES, REDEEMABLE NONCONTROLLING INTERESTS AND EQUITY
Mortgage and other indebtedness	4,680,521	4,745,683
Accounts payable and accrued liabilities	302,946	358,874
Total liabilities	4,983,467	5,104,557
Commitments and contingencies (Notes 5 and 11)
Redeemable noncontrolling interests:
Redeemable noncontrolling partnership interests	43,615	40,248
Redeemable noncontrolling preferred joint venture interest	423,719	423,834
Total redeemable noncontrolling interests	467,334	464,082
Preferred stock, $.01 par value, 15,000,000 shares authorized:
7.375% Series D Cumulative Redeemable Preferred Stock, 1,815,000 shares outstanding	18	18
6.625% Series E Cumulative Redeemable Preferred Stock, 690,000 shares outstanding	7	7
Common stock, $.01 par value, 350,000,000 shares authorized, 163,387,752 and 161,309,652 issued and outstanding in 2013 and 2012, respectively	1,634	1,613
Additional paid-in capital	1,804,108	1,773,630
Accumulated other comprehensive income	7,850	6,986
Dividends in excess of cumulative earnings	(472,184)	(453,561)
Total shareholders' equity	1,341,433	1,328,693
Noncontrolling interests	197,843	192,404
Total equity	1,539,276	1,521,097
Total Liabilities, Redeemable Noncontrolling Interests and Equity	$ 6,990,077	$ 7,089,736