Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Assets:
Operating real estate, net of accumulated depreciation of $1,916,505 and $1,878,681, respectively	$ 7,291,039		$ 7,146,845
Investments and advances in real estate joint ventures	1,198,424		1,257,010
Real estate under development	97,990		97,818
Other real estate investments	266,584		274,641
Mortgages and other financing receivables	23,475		30,243
Cash and cash equivalents	268,911		148,768
Marketable securities	63,312	[1]	62,766	[1]
Accounts and notes receivable	158,528		164,326
Other assets	465,434		481,213
Total assets	9,833,697		9,663,630
Liabilities:
Notes payable	3,305,065	[2]	3,186,047	[2]
Mortgages payable	1,075,281	[3]	1,035,354	[3]
Dividends payable	104,670		104,496
Other liabilities	515,032		482,054
Total liabilities	5,000,048		4,807,951
Redeemable noncontrolling interests	91,319		86,153
Preferred stock, $1.00 par value, authorized 5,961,200 shares, 102,000 shares issued and outstanding (in series)
Aggregate liquidation preference $975,000	102		102
Common stock, $.01 par value, authorized 750,000,000 shares issued and outstanding 410,506,232 and 409,731,058 shares, respectively	4,105		4,097
Paid-in capital	5,705,869		5,689,258
Cumulative distributions in excess of net income	(1,015,995)		(996,058)
Accumulated other comprehensive income	(76,870)		(64,982)
Total stockholders' equity	4,617,211		4,632,417
Noncontrolling interest	125,119		137,109
Total equity	4,742,330		4,769,526
Total liabilities and equity	$ 9,833,697		$ 9,663,630

[1] As of March 31, 2014 and December 31, 2013, the Company determined that $60.5 million and $59.7 million, respectively, of the Marketable securities estimated fair value were classified within Level 1 of the fair value hierarchy and the remaining $2.7 million and $3.1 million, respectively, were classified within Level 3 of the fair value hierarchy.

[2] The Company determined that its valuation of Notes payable was classified within Level 2 of the fair value hierarchy.

[3] The Company determined that its valuation of Mortgages payable was classified within Level 3 of the fair value hierarchy.