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	536,251						521,244		15,007
Dividends on common shares, value	(254,099)						(254,099)
Dividends on preferred shares, value	(30,116)						(30,116)
Proceeds from the issuance of shares, shares				8,850
Proceeds from the issuance of shares, value	214,538			214,538
Common shares issued:
Upon redemption of Class A units, at redemption value, shares					401
Upon redemption of Class A units, at redemption value, value	35,208				16	35,192
Under employees' share option plan, shares					343
Under employees' share option plan, value	20,051				14	20,434	(397)
Under dividend reinvestment plan, shares					10
Under dividend reinvestment plan, value	883				0	883
Limited partners' contributions:
Limited partners' contribution		109,241	364							109,241	364
Distributions:
Distributions to Limited Partners		(20,796)	(15,604)							(20,796)	(15,604)
Conversion Of Series A Preferred Shares To Common Shares, Shares				(1)	2
Conversion of Series A preferred shares to common shares, value	0			(75)	0	75
Deferred compensation shares and options, shares					10
Deferred compensation shares and options, value	5,122				0	5,122
Change in unrealized net gain on securities available-for-sale	40,844							40,844
Pro rata share of other comprehensive income of nonconsolidated subsidiaries	26,365							26,365
Change in value of interest rate swap	(18,034)							(18,034)
Adjustment to carry redeemable Class A units at redemption value	(104,693)					(104,693)
Redeemable noncontrolling interests' share of above adjustments	(3,104)							(3,104)
Other	(5,302)			(105)		(4,518)	(10)	(5,045)	4,376
Ending balance, value at Jun. 30, 2011	7,367,524			997,446	7,347	6,885,223	(1,244,254)	114,479	607,283
Ending balance, shares at Jun. 30, 2011				41,189	184,428
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	314,137						289,819		24,318
Dividends on common shares, value	(256,119)						(256,119)
Dividends on preferred shares, value	(35,574)						(35,574)
Common shares issued:
Upon redemption of Class A units, at redemption value, shares					303
Upon redemption of Class A units, at redemption value, value	24,976				12	24,964
Under employees' share option plan, shares					412
Under employees' share option plan, value	(7,573)				16	8,800	(16,389)
Under dividend reinvestment plan, shares					10
Under dividend reinvestment plan, value	843				1	842
Limited partners' contributions:
Limited partners' contribution		108,319	30							108,319	30
Distributions:
Distributions to Limited Partners		(44,910)								(44,910)
Conversion Of Series A Preferred Shares To Common Shares, Shares				(2)	3
Conversion of Series A preferred shares to common shares, value	0			(105)		105
Deferred compensation shares and options, shares					7
Deferred compensation shares and options, value	8,145				0	8,484	(339)
Change in unrealized net gain on securities available-for-sale	(220,525)							(220,525)
Pro rata share of other comprehensive income of nonconsolidated subsidiaries	(26,254)							(26,254)
Change in value of interest rate swap	(6,002)							(6,002)
Adjustment to carry redeemable Class A units at redemption value	(110,581)					(110,581)
Redeemable noncontrolling interests' share of above adjustments	15,894							15,894
Other	372			0		0	2	373	(3)
Ending balance, value at Jun. 30, 2012	$ 7,273,625			$ 1,021,555	$ 7,402	$ 7,059,872	$ (1,420,304)	$ (162,785)	$ 767,885
Ending balance, shares at Jun. 30, 2012				42,185	185,815