Consolidated Balance Sheets (USD $)	Dec. 31, 2012	Dec. 31, 2011
Assets:
Land	$ 2,024,300,000	$ 1,945,045,000
Building and improvements	6,825,724,000	6,646,490,000
	8,850,024,000	8,591,535,000
Less: accumulated depreciation and amortization	(1,745,462,000)	(1,693,090,000)
	7,104,562,000	6,898,445,000
Real estate under development	97,263,000	179,722,000
Real estate, net	7,201,825,069	7,078,167,000
Investments and advances in real estate joint ventures	1,428,155,000	1,404,214,000
Other real estate investments	317,557,000	344,131,000
Mortgages and other financing receivables	70,704,000	102,972,000
Cash and cash equivalents	141,875,000	112,882,000
Marketable securities	36,541,000	33,540,000
Accounts and notes receivable	161,113,000	164,053,000
Deferred charges and prepaid expenses	171,373,000	161,974,000
Other assets	211,664,000	226,829,000
Total assets	9,740,807,000	9,628,762,000
Liabilities:
Notes payable	3,192,127,000	2,983,886,000
Mortgages payable	1,003,190,000	1,085,371,000
Construction loans payable		45,128,000
Accounts payable and accrued expenses	111,881,000	125,544,000
Dividends payable	96,518,000	92,159,000
Other liabilities	323,535,000	321,457,000
Total liabilities	4,727,251,000	4,653,545,000
Redeemable noncontrolling interests	81,076,000	95,074,000
Stockholders' equity:
Preferred stock, $1.00 par value, authorized 5,961,200 and 5,146,000 shares, respectively, 102,000 and 954,000 shares issued and outstanding (in series), respectively, Aggregate liquidation preference $975,000 and $810,000, respectively	102,000	954,000
Common stock, $.01 par value, authorized 750,000,000 shares issued and outstanding 407,782,102 and 406,937,830 shares, respectively	4,078,000	4,069,000
Paid-in capital	5,651,170,000	5,492,022,000
Cumulative distributions in excess of net income	(824,008,000)	(702,999,000)
Accumulated other comprehensive income	(66,182,000)	(107,660,000)
Total stockholders' equity	4,765,160,000	4,686,386,000
Noncontrolling interests	167,320,000	193,757,000
Total equity	4,932,480,000	4,880,143,000
Total liabilities and equity	$ 9,740,807,000	$ 9,628,762,000