CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	PREFERRED SHARES	COMMON SHARES, $0.01 PAR VALUE	PAID IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME	OPERATING PARTNERSHIP	Partially Owned Properties [Member]
Beginning Balance, Noncontrolling Interest at Dec. 31, 2011	$ 193,842						$ 119,536	$ 74,306
Beginning Balance, Parent at Dec. 31, 2011	5,669,015	200,000	2,975	5,047,186	615,572	(196,718)
Redemption of Preferred Shares Preference Units	(150,000)
Stock Repurchased And Retired	0
Common Share Issuance:
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner			3	8,557			(8,560)
Issuance of Common Shares	192,300		32	192,264
Exercise of share options			15	46,766
Employee Share Purchase Plan (ESPP)			1	4,943
Share-based employee compensation expense:
Restricted shares			1	6,998
Share options				9,854
ESPP discount				884
Offering costs				(2,860)
Acquisition Noncontrolling Interests Partially Owned Properties				1,219				(1,306)
Supplemental Executive Retirement Plan (SERP)				(407)
Change in market value	(8,866)			8,866
Adjustment for Noncontrolling Interests ownership in Operating Partnership				35,403			(35,403)
Net income attributable to controlling interests	474,702				474,702
Common Share distributions					(305,108)
Preferred Share distributions					(9,319)
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding (losses) arising during the period	(12,337)					(12,337)
Losses reclassified into earnings from other comprehensive income	10,907					10,907
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	394					394
Issuance Of OP Units To Noncontrolling Interests	66,606
Issuance of LTIP Units to Noncontrolling Interests							5
Equity Compensation associated with Noncontrolling Interests							4,759
Net Income (Loss) Attributable to Noncontrolling Interest							21,646	457
Distributions to Noncontrolling Interests							(14,258)	(4,775)
Change in carrying value	6,681						(6,681)
Contributions by Noncontrolling Interests								5,992
Premium on Redemption of Preferred Shares Cash	(21)				(21)
Premium on Redemption of Preferred Shares Preference Units Original Issuance	(5,129)				(5,129)
Stockholders' Equity, Other								754
Ending Balance, Noncontrolling Interest at Sep. 30, 2012	223,078						147,650	75,428
Ending Balance, Parent at Sep. 30, 2012	$ 5,990,772	$ 50,000	$ 3,027	$ 5,364,802	$ 770,697	$ (197,754)