CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Unaudited) (USD $) In Thousands	Total	PREFERRED SHARES	COMMON SHARES, $0.01 PAR VALUE	PAID IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE (LOSS)	PARTIALLY OWNED PROPERTIES	OPERATING PARTNERSHIP	OPERATING PARTNERSHIP ACCUMULATED OTHER COMPREHENSIVE (LOSS)	OPERATING PARTNERSHIP PARTIALLY OWNED PROPERTIES	OPERATING PARTNERSHIP General Partner [Member]	OPERATING PARTNERSHIP Limited Partner [Member]
Beginning Balance at Dec. 31, 2010	$ 5,208,576	$ 200,000	$ 2,902	$ 4,741,521	$ 203,581	$ (57,818)	$ 7,991	$ 110,399
Common Share Issuance:
Conversion of OP Units into Common Shares			3	8,092				(8,095)
Issuance of Common Shares			30	154,478
Exercise of share options			29	94,344							94,373
Employee Share Purchase Plan (ESPP)			1	4,557							4,558
Conversion of restricted shares to LTIP Units			(1)	(3,933)				3,934			(3,934)	3,934
Share-based employee compensation expense:
Restricted shares			2	7,275
Share options				7,389							1,070
ESPP discount				1,070
Offering costs				(2,770)							(2,770)
Supplemental Executive Retirement Plan (SERP)				10,198							10,198
Acquisition of Noncontrolling Interests - Partially Owned Properties				(4,784)			(8,025)			(8,025)	(4,784)
Change in market value of Redeemable Noncontrolling Interests - Operating Partnership	(16,023)			16,023
Net income attributable to controlling interests	791,103				791,103			827,378
Common Share distributions					(299,383)
Preferred Share distributions					(10,399)
Accumulated other comprehensive (loss) - derivative instruments:
Unrealized holding (losses) arising during the period	(130,367)					(130,367)		(130,367)	(130,367)
Accumulated other comprehensive income	2,842					2,842		2,842	2,842
Accumulated other comprehensive income - other instruments:
Unrealized holding (losses) arising during the period	311					311		311
Equity compensation associated with Noncontrolling Interests								2,734				2,734
Net income attributable to Noncontrolling Interests	827,796						418	827,796
Contributions by Noncontrolling Interests							64			64
Distributions to Noncontrolling Interests							(922)	(13,777)		(922)
Change in carrying value of Redeemable Noncontrolling Interests - Operating Partnership	(11,281)							(11,281)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				(597)				597
Other							(1,240)
Ending Balance at Sep. 30, 2011	5,854,771	200,000	2,966	5,032,863	684,902	(185,032)	(1,714)	120,786
Beginning Balance at Jun. 30, 2011
Share-based employee compensation expense:
Net income attributable to controlling interests	107,848							112,590
Accumulated other comprehensive (loss) - derivative instruments:
Unrealized holding (losses) arising during the period	(105,248)							(105,248)
Accumulated other comprehensive income	951							951
Accumulated other comprehensive income - other instruments:
Unrealized holding (losses) arising during the period	(182)							(182)
Net income attributable to Noncontrolling Interests	112,977							112,977
Ending Balance at Sep. 30, 2011	$ 5,854,771	$ 200,000						$ 120,786