Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows from Operating Activities:
Net income	$ 694,541,000	$ 740,000,000	$ 708,031,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization (including amortization of deferred financing costs)	557,888,000	580,990,000	556,312,000
Equity in net income of partially owned entities including Toys "R" Us	(423,126,000)	(118,612,000)	(92,493,000)
Net gain on sales of real estate	(245,799,000)	(51,623,000)	(2,506,000)
Distributions of income from partially owned entities	226,172,000	93,635,000	61,037,000
Non-cash impairment loss on J.C. Penney owned shares	224,937,000	0	0
Impairment losses, write-off of tenant buy-outs and litigation loss accrual	133,977,000	58,173,000	137,367,000
Loss (income) from the mark-to-market of J.C. Penney derivative position	75,815,000	(12,984,000)	(130,153,000)
Straight-lining of rental income	(69,648,000)	(45,788,000)	(76,926,000)
Return of capital from Real Estate Fund investments	63,762,000	0	0
Net realized and unrealized gains on Real Estate Fund assets	(55,361,000)	(17,386,000)	0
Amortization of below-market leases, net	(54,359,000)	(63,044,000)	(66,202,000)
Other non-cash adjustments	52,082,000	27,325,000	36,352,000
Gain on sale of Canadian Trade Shows	(31,105,000)	0	0
Net gain on disposition of wholly owned and partially owned assets	(13,347,000)	(15,134,000)	(81,432,000)
Net gain on extinguishment of debt	0	(83,907,000)	(97,728,000)
Mezzanine loans loss reversal and net gain on disposition	0	(82,744,000)	(53,100,000)
Recognition of disputed account receivable from Stop & Shop	0	(23,521,000)	0
Interest received on repayment of mezzanine loan	0	0	40,467,000
Changes in operating assets and liabilities:
Real Estate Fund investments	(262,537,000)	(184,841,000)	(144,423,000)
Tenant and other receivables, net	(23,271,000)	8,869,000	2,019,000
Prepaid assets	(10,549,000)	(7,779,000)	6,321,000
Other assets	(46,573,000)	(89,186,000)	(68,305,000)
Accounts payable and accrued expenses	21,595,000	(28,699,000)	2,645,000
Other liabilities	9,955,000	18,755,000	33,803,000
Net cash provided by operating activities	825,049,000	702,499,000	771,086,000
Cash Flows from Investing Activities:
Acquisitions of real estate and other	(673,684,000)	(90,858,000)	(173,413,000)
Proceeds from sales of real estate and related investments	445,683,000	140,186,000	127,736,000
Additions to real estate	(205,652,000)	(165,680,000)	(144,794,000)
Funding of J.C. Penney derivative collateral	(191,330,000)	(43,850,000)	(12,500,000)
Development costs and construction in progress	(156,873,000)	(93,066,000)	(156,775,000)
Distributions of capital from partially owned entities	144,502,000	318,966,000	51,677,000
Investments in partially owned entities	(134,994,000)	(571,922,000)	(165,170,000)
Return of J.C. Penney derivative collateral	134,950,000	56,350,000	0
Investments in mezzanine loans receivable and other	(94,094,000)	(98,979,000)	(85,336,000)
Restricted cash	(75,138,000)	126,380,000	138,586,000
Proceeds from sales of, and return of investment in, marketable securities	60,258,000	70,418,000	280,462,000
Proceeds from the sale of Canadian Trade Shows	52,504,000	0	0
Proceeds from sales and repayments of mezzanine loans receivable and other	38,483,000	187,294,000	70,762,000
Proceeds from the repayment of loan to officer	13,123,000	13,123,000	0
Loan to officer	0	(13,123,000)	0
Purchases of marketable securities including J.C. Penney common shares and other	0	0	(491,596,000)
Proceeds from maturing short-term investments	0	0	40,000,000
Net cash used in investing activities	(642,262,000)	(164,761,000)	(520,361,000)
Cash Flows from Financing Activities:
Proceeds from borrowings	3,593,000,000	3,412,897,000	2,481,883,000
Repayments of borrowings	(2,747,694,000)	(3,740,327,000)	(1,564,143,000)
Dividends paid on common shares	(699,318,000)	(508,745,000)	(474,299,000)
Proceeds from the issuance of preferred shares	290,971,000	238,842,000	0
Purchases of outstanding preferred units and shares	(243,300,000)	(28,000,000)	(78,954,000)
Contributions from noncontrolling interests	213,132,000	204,185,000	103,831,000
Distributions to noncontrolling interests	(104,448,000)	(116,510,000)	(53,842,000)
Dividends paid on preferred shares	(73,976,000)	(61,464,000)	(55,669,000)
Debt issuance and other costs	(39,073,000)	(47,395,000)	(14,980,000)
Repurchase of shares related to stock compensation agreements and related tax withholdings	(30,168,000)	(964,000)	(25,660,000)
Proceeds received from exercise of employee share options	11,853,000	25,507,000	26,993,000
Acquisition of convertible senior debentures and senior unsecured notes	0	0	(440,575,000)
Net cash provided by (used in) financing activities	170,979,000	(621,974,000)	(95,415,000)
Net increase (decrease) in cash and cash equivalents	353,766,000	(84,236,000)	155,310,000
Cash and cash equivalents at beginning of period	606,553,000	690,789,000	535,479,000
Cash and cash equivalents at end of period	960,319,000	606,553,000	690,789,000
Supplemental Disclosure Of Cash Flow Information [Abstract]
Cash payments for interest (net of amounts capitalized of $16,801, $1,197 and $864)	491,869,000	531,174,000	549,327,000
Cash payments for income taxes	21,709,000	26,187,000	23,960,000
Non-Cash Investing and Financing Activities:
Adjustments to carry redeemable Class A units at redemption value	(52,117,000)	98,092,000	(191,826,000)
Contribution of mezzanine loan receivable to joint venture	0	73,750,000	0
Write-off of fully depreciated assets	(177,367,000)	(72,279,000)	(63,007,000)
Common shares issued upon redemption of Class A units at redemption value	89,762,000	64,830,000	126,764,000
Change in unrealized net gain on securities available-for-sale	(283,649,000)	41,657,000	55,891,000
Financing assumed in acquisitions	0	0	102,616,000
Financings transferred in dispositions	(163,144,000)	0	0
L.A. Mart seller financing	35,000,000	0	0
Marriott Marquis Times Square - retail and signage capital lease: Asset (included in development costs and construction in progress)	240,000,000
Marriott Marquis Times Square Hotel - retail and signage capital lease: Liability (included in other liabilities)	(240,000,000)	0	0
Increase in assets and liabilities resulting from the consolidation of investments previously accounted for on the equity method:
Real Estate, net	342,919,000	0	102,804,000
Notes and mortgages payable	334,225,000	0	57,563,000
Decrease in assets and liabilities resulting from deconsolidation of investments that were previously consolidated:
Real Estate, Net	0	(145,333,000)	(401,857,000)
Notes and Mortgages Payable	0	(232,502,000)	(316,490,000)
Like Kind Properties Acquired [Member]
Non-Cash Investing and Financing Activities:
Like-kind exchange of real estate	230,913,000	21,999,000	0
Like Kind Properties Sold [Member]
Non-Cash Investing and Financing Activities:
Like-kind exchange of real estate	(230,913,000)	(45,625,000)	0
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	(14,859,000)	(48,540,000)	(71,624,000)
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	$ (408,267,000)	$ (70,072,000)	$ (20,869,000)