Consolidated Statements of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Real Estate Funds [Member]	All Other Except Real Estate Fund [Member]	Preferred Shares	Common Shares	Additional Capital	Earnings Less Than Distributions	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interests	Non-controlling Interests Real Estate Funds [Member]	Non-controlling Interests All Other Except Real Estate Fund [Member]
Beginning balance, Value at Dec. 31, 2009	$ 6,649,406			$ 823,686	$ 7,218	$ 6,961,007	$ (1,577,591)	$ 28,449	$ 406,637
Beginning balance, Shares at Dec. 31, 2009				33,952	181,214
Net income (loss)	652,803						647,883		4,920
Dividends paid on common shares, Value	(474,299)						(474,299)
Dividends paid on preferred shares, Value	(55,669)						(55,669)
Redemption of preferred shares, Shares				(1,600)
Redemption of preferred shares, Value	(35,600)			(39,982)			4,382
Common shares issued:
Upon redemption of Class A units, at redemption value, Shares					1,548
Upon redemption of Class A units, at redemption value, Value	126,764				62	126,702
Under Omnibus share plan, Shares					812
Under Omnibus share plan, Value	(261)				33	25,290	(25,584)
Under dividend reinvestment plan, Shares					22
Under dividend reinvestment plan, Value	1,657				1	1,656
Contributions:
Contributions		93,583	8,783							93,583	8,783
Distribution:
Conversion Of Series A preferred shares to common shares, Shares				(12)	18
Conversion of Series A preferred shares to common shares, Value	0			(616)	1	615
Deferred compensation shares and options, Shares					48
Deferred compensation shares and options, Value	9,347				2	9,345
Change in unrealized net gain on securities available-for-sale	55,891							55,891
Gain on sale of securities available-for-sale	(22,604)							(22,604)
Pro rata share of other comprehensive income of nonconsolidated subsidiaries	11,853							11,853
Adjustments to carry redeemable Class A units at redemption value	(191,826)					(191,826)
Discount on redemption of preferred shares and units	4,382
Other	577					(61)	2	(136)	772
Ending balance, Value at Dec. 31, 2010	6,830,405			783,088	7,317	6,932,728	(1,480,876)	73,453	514,695
Ending balance, Shares at Dec. 31, 2010				32,340	183,662
Net income (loss)	684,088						662,302		21,786
Dividends paid on common shares, Value	(508,745)						(508,745)
Dividends paid on preferred shares, Value	(65,694)						(65,694)
Proceeds from the issuance of shares, Shares				9,850
Proceeds from the issuance of shares, Value	238,842			238,842
Common shares issued:
Upon redemption of Class A units, at redemption value, Shares					798
Upon redemption of Class A units, at redemption value, Value	64,830				32	64,798
Under Omnibus share plan, Shares					590
Under Omnibus share plan, Value	10,439				23	23,705	(13,289)
Under dividend reinvestment plan, Shares					21
Under dividend reinvestment plan, Value	1,772				1	1,771	0
Contributions:
Contributions		203,407	778							203,407	778
Distribution:
Distributions		(49,422)	(15,604)							(49,422)	(15,604)
Conversion Of Series A preferred shares to common shares, Shares				(3)	5
Conversion of Series A preferred shares to common shares, Value	0			(165)		165
Deferred compensation shares and options, Shares					4
Deferred compensation shares and options, Value	10,085				0	10,608	(523)
Change in unrealized net gain on securities available-for-sale	41,657							41,657
Gain on sale of securities available-for-sale	(5,020)							(5,020)
Pro rata share of other comprehensive income of nonconsolidated subsidiaries	12,859							12,859
Change in value of interest rate swap	(43,704)							(43,704)
Adjustments to carry redeemable Class A units at redemption value	98,092					98,092
Redeemable noncontrolling interests' share of above adjustments	(271)							(271)
Discount on redemption of preferred shares and units	5,000
Other	(347)			(105)		(4,609)	5,121	(5,245)	4,491
Ending balance, Value at Dec. 31, 2011	7,508,447			1,021,660	7,373	7,127,258	(1,401,704)	73,729	680,131
Ending balance, Shares at Dec. 31, 2011				42,187	185,080
Net income (loss)	649,278						617,260		32,018
Dividends paid on common shares, Value	(699,318)						(699,318)
Dividends paid on preferred shares, Value	(76,937)						(76,937)
Proceeds from the issuance of shares, Shares				12,000
Proceeds from the issuance of shares, Value	290,971			290,971
Redemption of preferred shares, Shares				(3,000)
Redemption of preferred shares, Value	(72,248)			(72,248)
Common shares issued:
Upon redemption of Class A units, at redemption value, Shares					1,121
Upon redemption of Class A units, at redemption value, Value	89,762				45	89,717
Under Omnibus share plan, Shares					434
Under Omnibus share plan, Value	(6,850)				18	9,521	(16,389)
Under dividend reinvestment plan, Shares					29
Under dividend reinvestment plan, Value	2,307				1	2,306
Upon acquisition of real estate, Shares					64
Upon acquisition of real estate, Value	5,124				3	5,121
Contributions:
Contributions		195,029	18,103							195,029	18,103
Distribution:
Distributions		(48,138)	(59)							(48,138)	(59)
Conversion Of Series A preferred shares to common shares, Shares				(2)	3
Conversion of Series A preferred shares to common shares, Value	0			(105)	0	105
Deferred compensation shares and options, Shares					4
Deferred compensation shares and options, Value	13,054				0	13,527	(473)
Change in unrealized net gain on securities available-for-sale	(283,649)							(283,649)
Gain on sale of securities available-for-sale	(3,582)							(3,582)
Non-cash impairment on J.C. Penney owned shares	224,937							224,937
Pro rata share of other comprehensive income of nonconsolidated subsidiaries	(31,758)							(31,758)
Change in value of interest rate swap	(5,659)							(5,659)
Adjustments to carry redeemable Class A units at redemption value	(52,117)					(52,117)
Redeemable noncontrolling interests' share of above adjustments	6,707							6,707
Discount on redemption of preferred shares and units	8,948						8,948
Consolidation of a partially owned entity	176,132								176,132
Other	(4,340)			0		0	(4,662)	329	(7)
Ending balance, Value at Dec. 31, 2012	$ 7,904,144			$ 1,240,278	$ 7,440	$ 7,195,438	$ (1,573,275)	$ (18,946)	$ 1,053,209
Ending balance, Shares at Dec. 31, 2012				51,185	186,735