Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Assets:
Operating real estate, net of accumulated depreciation of $1,835,280 and $1,745,462, respectively	$ 7,284,151		$ 7,104,562
Investments and advances in real estate joint ventures	1,392,418		1,428,155
Real estate under development	96,950		97,263
Other real estate investments	316,043		317,557
Mortgages and other financing receivables	74,088		70,704
Cash and cash equivalents	156,450		141,875
Marketable securities	71,009	[1]	36,541	[1]
Accounts and notes receivable	160,398		171,540
Other assets	436,964		383,037
Total assets	9,988,471		9,751,234
Liabilities:
Notes payable	3,284,014	[2]	3,192,127	[2]
Mortgages payable	1,180,760	[3]	1,003,190	[3]
Dividends payable	98,326		96,518
Other liabilities	473,604		445,843
Total liabilities	5,036,704		4,737,678
Redeemable noncontrolling interests	85,486		81,076
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 409,616,877 and 407,782,102 shares, respectively	4,096		4,078
Paid-in capital	5,685,943		5,651,170
Cumulative distributions in excess of net income	(906,070)		(824,008)
Accumulated other comprehensive income	(61,798)		(66,182)
Total stockholders' equity	4,722,273		4,765,160
Noncontrolling interests	144,008		167,320
Total equity	4,866,281		4,932,480
Total liabilities and equity	$ 9,988,471		$ 9,751,234

[1] As of June 30, 2013 and December 31, 2012, the Company determined that $68.0 million and $33.4 million, respectively, of the marketable securities estimated fair value were classified within Level 1 of the fair value hierarchy and the remaining $3.3 million and $3.4 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.