Consolidated Statements of Changes in Equity (USD $) In Thousands	Total	Preferred Shares	Common Shares	Additional Capital	Earnings Less Than Distributions	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interests	Real Estate Fund [Member]	Real Estate Fund [Member] Non-controlling Interests	All Other Except Real Estate Fund [Member]	All Other Except Real Estate Fund [Member] Non-controlling Interests
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	287,852				286,658		1,194
Dividends paid on common shares, value	(236,279)				(236,279)
Dividends paid on preferred shares, value	(28,533)				(28,533)
Common shares issued:
Upon redemption of Class A units, at redemption value, shares			495
Upon redemption of Class A units, at redemption value, value	35,711		20	35,691
Under employees' share option plan, shares			548
Under employees' share option plan, value	(16,422)		22	8,989	(25,433)
Under dividend reinvestment plan, shares			12
Under dividend reinvestment plan, value	802		1	801
Limited partners' contributions:
Conversion Of Series A Preferred Shares To Common Shares, Shares		(3)	4
Conversion of Series A preferred shares to common shares, value	0	(152)	0	152
Deferred compensation shares and options, shares			17
Deferred compensation shares and options, value	3,906		1	3,905
Change in unrealized net gain or (loss) on sale of securities available for sale	25,531					25,531
Our share of partially owned entities OCI adjustments	(15,965)					(15,965)
Change in value of interest rate caps	0
Adjustment to carry redeemable Class A units at redemption value	(66,075)			(66,075)
Other	(1,021)			(60)	2	(418)	(545)
Ending balance, value at Jun. 30, 2010	6,638,913	823,534	7,262	6,944,410	(1,581,176)	37,597	407,286
Ending balance, shares at Jun. 30, 2010		33,949	182,290
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 paid on common shares, value	(254,099)				(254,099)
Dividends paid 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			883
Limited partners' contributions:
Limited partners' contribution								109,241	109,241	364	364
Conversion Of Series A Preferred Shares To Common Shares, Shares		(1)	2
Conversion of Series A preferred shares to common shares, value	0	(75)		75
Deferred compensation shares and options, shares			10
Deferred compensation shares and options, value	5,122			5,122
Change in unrealized net gain or (loss) on sale of securities available for sale	40,844					40,844
Our share of partially owned entities OCI adjustments	26,365					26,365
Change in value of interest rate caps	(18,034)					(18,034)
Adjustment to carry redeemable Class A units at redemption value	(104,693)			(104,693)
Distributions to Limited Partners								(20,796)	(20,796)	(15,604)	(15,604)
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