Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash Flows from Operating Activities:
Net income	$ 288,927	$ 280,264
Adjustments to reconcile net income to net cash provided by operating activities:
Net gains on sale of real estate	(202,329)	(55,817)
Depreciation and amortization (including amortization of deferred financing costs)	148,918	145,304
Return of capital from Real Estate Fund investments	56,664	0
Non-cash impairment loss on J.C. Penney owned shares	39,487	0
Net loss on disposition of wholly owned and partially owned assets	36,724	0
Equity in net income of partially owned entities including Toys "R" Us	(22,525)	(136,131)
Loss (income) from the mark-to-market of J.C. Penney derivative position	22,540	(1,045)
Straight-lining of rental income	(18,868)	(21,808)
Other non-cash adjustments	18,569	7,795
Amortization of below-market leases, net	(16,815)	(13,813)
Net unrealized gain on Real Estate Fund investments	(13,516)	(6,844)
Distributions of income from partially owned entities	10,627	14,194
Impairment losses	1,514	0
Changes in operating assets and liabilities:
Real Estate Fund investments	(13,668)	28,980
Accounts receivable, net	51,514	(19,386)
Prepaid assets	67,814	51,202
Other assets	(15,326)	(9,245)
Accounts payable and accrued expenses	(21,908)	40,609
Other liabilities	(3,416)	2,844
Net cash provided by operating activities	414,927	307,103
Cash Flows from Investing Activities:
Proceeds from sales of real estate and related investments	499,369	306,022
Proceeds from sales of marketable securities	160,300	0
Funding of J.C. Penney derivative collateral	(58,522)	0
Return of J.C. Penney derivative collateral	38,900	0
Additions to real estate	(57,460)	(44,052)
Investments in partially owned entities	(39,892)	(46,732)
Development costs and construction in progress	(35,334)	(20,614)
Restricted cash	14,149	(19,355)
Distributions of capital from partially owned entities	5,544	4,203
Proceeds from Collection of Notes Receivable	631	554
Acquisitions of real estate and other	0	(21,054)
Proceeds from the repayment of loan to officer	0	13,123
Net cash provided by investing activities	527,685	172,095
Cash Flows from Financing Activities:
Repayments of borrowings	(2,529,836)	(884,679)
Proceeds from borrowings	1,499,375	625,000
Proceeds from the issuance of preferred shares	290,710	0
Purchases of outstanding preferred units and shares	(262,500)	0
Distributions to noncontrolling interests	(172,142)	(34,092)
Dividends paid on common shares	(136,342)	(127,973)
Contributions from noncontrolling interests	24,566	0
Dividends paid on preferred shares	(23,161)	(17,789)
Debt issuance and other costs	(9,080)	(9,822)
Proceeds received from exercise of employee share options	1,607	7,997
Repurchase of shares related to stock compensation agreements and related tax withholdings	(305)	(30,034)
Net cash used in financing activities	(1,317,108)	(471,392)
Net (decrease) increase in cash and cash equivalents	(374,496)	7,806
Cash and cash equivalents at beginning of period	960,319	606,553
Cash and cash equivalents at end of period	585,823	614,359
Supplemental Disclosure Of Cash Flow Information [Abstract]
Cash payments for interest, excluding capitalized interest of $8,260 and $16	116,141	117,282
Cash payments for income taxes	1,825	2,563
Non-Cash Investing and Financing Activities:
Change in unrealized net gain on securities available-for-sale	148,789	12,693
Adjustments to carry redeemable Class A units at redemption value	(44,998)	(96,061)
Common shares issued upon redemption of Class A units, at redemption value	13,404	13,028
Write-off of fully depreciated assets	(11,730)	(37,890)
Toys R Us [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in net income of partially owned entities including Toys "R" Us	(1,759)	(116,471)
All Equity Method Investees Excluding Toys [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in net income of partially owned entities including Toys "R" Us	$ (20,766)	$ (19,660)