CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (USD $)	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	$ 193,842,000						$ 119,536,000	$ 74,306,000
Beginning Balance, Parent at Dec. 31, 2011	5,669,015,000	200,000,000	2,975,000	5,047,186,000	615,572,000	(196,718,000)
Stock Repurchased And Retired	0
Common Share Issuance:
Conversion of OP Units held by Noncontrolling Interests into OP Units held by General Partner			2,000	4,752,000			(4,754,000)
Issuance of Common Shares	123,601,393		21,000	123,580,000
Exercise of share options			10,000	31,271,000
Employee Share Purchase Plan (ESPP)			1,000	4,522,000
Share-based employee compensation expense:
Restricted shares			1,000	5,115,000
Share options				7,976,000
ESPP discount				809,000
Offering costs				(1,907,000)
Acquisition Noncontrolling Interests Partially Owned Properties				1,219,000				(1,306,000)
Supplemental Executive Retirement Plan (SERP)				(5,473,000)
Change in market value	32,391,000			(32,391,000)
Adjustment for Noncontrolling Interests ownership in Operating Partnership				39,429,000			(39,429,000)
Net income attributable to controlling interests	248,563,000				248,563,000
Common Share distributions					(202,967,000)
Preferred Share distributions					(6,933,000)
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding (losses) arising during the period	(8,642,000)					(8,642,000)
Losses reclassified into earnings from other comprehensive income	(7,203,000)					7,203,000
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	82,000					82,000
Issuance Of OP Units To Noncontrolling Interests	66,606,000
Issuance of LTIP Units to Noncontrolling Interests							5,000
Equity Compensation associated with Noncontrolling Interests							4,211,000
Net Income (Loss) Attributable to Noncontrolling Interest							11,150,000	769,000
Distributions to Noncontrolling Interests							(9,396,000)	(2,258,000)
Change in carrying value	3,408,000						(3,408,000)
Contributions by Noncontrolling Interests								2,935,000
Ending Balance, Noncontrolling Interest at Jun. 30, 2012	218,967,000						144,521,000	74,446,000
Ending Balance, Parent at Jun. 30, 2012	$ 5,885,258,000	$ 200,000,000	$ 3,010,000	$ 5,226,088,000	$ 654,235,000	$ (198,075,000)