Consolidated Statements of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Real Estate Fund [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 Fund [Member]	Non-controlling Interests All Other Except Real Estate Fund [Member]
Beginning balance, value at Dec. 31, 2010	$ 6,830,405			$ 783,088	$ 7,317	$ 6,932,728	$ (1,480,876)	$ 73,453	$ 514,695
Beginning balance, shares at Dec. 31, 2010				32,340	183,662
Net income	595,649						575,006		20,643
Dividends on common shares, value	(381,382)						(381,382)
Dividends on preferred shares, value	(47,905)						(47,905)
Proceeds from the issuance of shares, shares				9,850
Proceeds from the issuance of shares, value	239,037			239,037
Common shares issued:
Upon redemption of Class A units, at redemption value, shares					435
Upon redemption of Class A units, at redemption value, value	38,220				17	38,203
Under employees' share option plan, shares					369
Under employees' share option plan, value	21,221				15	21,603	(397)
Under dividend reinvestment plan, shares					15
Under dividend reinvestment plan, value	1,330				1	1,329
Limited partners' contributions:
Limited partners' contribution		109,241	364							109,241	364
Distributions:
Distributions to Limited Partners		(22,713)	(15,604)							(22,713)	(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)	0	165
Deferred compensation shares and options, shares					10
Deferred compensation shares and options, value	7,866				0	7,866
Change in unrealized net gain on securities available-for-sale	(120,334)							(120,334)
Pro rata share of other comprehensive income of nonconsolidated subsidiaries	26,477							26,477
Change in value of interest rate swap	(42,458)							(42,458)
Adjustment to carry redeemable Class A units at redemption value	114,628					114,628
Redeemable noncontrolling interests' share of above adjustments	8,957							8,957
Discount on redemption of preferred units	5,000						5,000
Other	(5,030)			(105)		(4,518)	149	(5,114)	4,558
Ending balance, value at Sep. 30, 2011	7,362,969			1,021,855	7,350	7,112,004	(1,330,405)	(59,019)	611,184
Ending balance, shares at Sep. 30, 2011				42,187	184,496
Beginning balance, value at Dec. 31, 2011	7,508,447			1,021,660	7,373	7,127,258	(1,401,704)	73,729	680,131
Beginning balance, shares at Dec. 31, 2011				42,187	185,080
Net income	562,053						531,125		30,928
Dividends on common shares, value	(384,353)						(384,353)
Dividends on preferred shares, value	(56,187)						(56,187)
Proceeds from the issuance of shares, shares				12,000
Proceeds from the issuance of shares, value	291,144			291,144
Redemption of preferred shares, shares				(3,000)
Redemption of preferred shares, value	(75,000)			(75,000)
Common shares issued:
Upon redemption of Class A units, at redemption value, shares					624
Upon redemption of Class A units, at redemption value, value	51,216				25	51,191
Under employees' share option plan, shares					414
Under employees' share option plan, value	(7,458)				16	8,915	(16,389)
Under dividend reinvestment plan, shares					15
Under dividend reinvestment plan, value	1,270				1	1,269
Limited partners' contributions:
Limited partners' contribution		120,606	140							120,606	140
Distributions:
Distributions to Limited Partners		(44,910)	(10)							(44,910)	(10)
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					7
Deferred compensation shares and options, value	10,670				0	11,009	(339)
Change in unrealized net gain on securities available-for-sale	(202,167)							(202,167)
Pro rata share of other comprehensive income of nonconsolidated subsidiaries	(38,861)							(38,861)
Change in value of interest rate swap	(8,868)							(8,868)
Adjustment to carry redeemable Class A units at redemption value	(63,657)					(63,657)
Redeemable noncontrolling interests' share of above adjustments	15,717							15,717
Discount on redemption of preferred units	11,700						11,700
Other	(2,638)			0		0	(2,971)	343	(10)
Ending balance, value at Sep. 30, 2012	$ 7,688,854			$ 1,237,699	$ 7,415	$ 7,136,090	$ (1,319,118)	$ (160,107)	$ 786,875
Ending balance, shares at Sep. 30, 2012				51,185	186,143