Earnings Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Aug. 18, 2011	Aug. 23, 2006
Numerator for net income per share - basic and diluted
(Loss) income from continuing operations		$ 128,433,000	$ 30,213,000	$ 12,654,000	$ 32,506,000	$ 28,274,000	$ 10,336,000	$ (13,322,000)	$ 311,555,000	$ 57,794,000	$ (103,108,000)
Income (Loss) Attributable to Noncontrolling Interest									(13,178,000)	(1,912,000)	5,419,000
Net (income) loss attributable to Noncontrolling Interests - Partially Owned Properties									(844,000)	(832,000)	726,000
Preferred distributions									(10,355,000)	(13,865,000)	(14,368,000)
Premium on redemption of Preferred Shares									(5,152,000)	0	0
Income (Loss) from Continuing Operations Attributable to Parent									282,026,000	41,185,000	(111,331,000)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									544,186,000	838,535,000	380,573,000
Numerator for net income per share - basic and diluted									826,212,000	879,720,000	269,242,000
Income from continuing operations									295,204,000	43,097,000
Discontinued operations, net		107,890,000	78,102,000	139,513,000	74,895,000	84,703,000	571,417,000	146,388,000	569,649,000	877,403,000	399,091,000
Denominator for net income per share - basic and diluted									864,853,000	920,500,000	269,242,000
Weighted Average Number of Shares Outstanding, Basic	310,398,000	301,336,000	300,193,000	298,805,000	295,990,000	295,831,000	294,663,000	292,895,000	302,701,000	294,856,000	282,888,000
Dilutive Op Units									13,853,000	13,206,000
Dilutive Securities, Effect on Basic Earnings Per Share, Including Options									3,212,000	4,003,000
Weighted average Common Shares outstanding	327,108,000	318,773,000	317,648,000	315,230,000	312,731,000	312,844,000	312,199,000	292,895,000	319,766,000	312,065,000	282,888,000
Net income available to Common Shares	$ 1.18	$ 0.73	$ 0.33	$ 0.47	$ 0.33	$ 0.35	$ 1.88	$ 0.42	$ 2.729	$ 2.984	$ 0.952
Net income per share - basic:
Income (loss) from continuing operations available to Common Shares									$ 0.932	$ 0.140	$ (0.393)
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share									$ 1.797	$ 2.844	$ 1.345
Net income available to Common Shares	$ 1.18	$ 0.73	$ 0.33	$ 0.47	$ 0.33	$ 0.35	$ 1.88	$ 0.42	$ 2.729	$ 2.984	$ 0.952
Net income per share - diluted:
Income (loss) from continuing operations available to Common Shares									$ 0.923	$ 0.138	$ (0.393)
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share									$ 1.782	$ 2.812	$ 1.345
Net income per share - diluted	$ 1.17	$ 0.72	$ 0.33	$ 0.47	$ 0.33	$ 0.35	$ 1.85	$ 0.42	$ 2.705	$ 2.950	$ 0.952
Distributions declared per Common Share outstanding									$ 1.780	$ 1.580	$ 1.470
Earnings Per Share (Textuals) [Abstract]
Convertible preferred shares									0	0	325,103
Convertible Notes, outstanding												482,500,000	650,000,000
Net (income) loss attributable to Noncontrolling Interests - Partially Owned Properties									(844,000)	(832,000)	726,000
Dividend preference units									(10,355,000)	(13,865,000)	(14,368,000)
Income Loss From Continuing Operations Available To Units									295,204,000	43,097,000	(116,750,000)
Net Income loss available to Op unitholders basic diluted numerator									864,853,000	920,500,000	282,341,000
Weighted Average Limited Partnership and General Partnership Units Outstanding, Basic									316,554,000	308,062,000	296,527,000
Weighted Average Number Of Limited Partnership And General Partnership Unit Outstanding Diluted									319,766,000	312,065,000	296,527,000
Distributions Per Limited Partnership and General Partnership Unit, Outstanding, Basic									$ 1.78	$ 1.58	$ 1.47
Operating Partnership [Member]
Numerator for net income per share - basic and diluted
(Loss) income from continuing operations	140,255,000	128,433,000	30,213,000	12,654,000	32,506,000	28,274,000	10,336,000	(13,322,000)
Discontinued operations, net	244,144,000	107,890,000	78,102,000	139,513,000	74,895,000	84,703,000	571,417,000	146,388,000
Net income available to Common Shares	$ 1.18	$ 0.73	$ 0.33	$ 0.47	$ 0.33	$ 0.35	$ 1.88	$ 0.42
Net income per share - basic:
Net income available to Common Shares	$ 1.18	$ 0.73	$ 0.33	$ 0.47	$ 0.33	$ 0.35	$ 1.88	$ 0.42
Net income per share - diluted:
Net income per share - diluted	$ 1.17	$ 0.72	$ 0.33	$ 0.47	$ 0.33	$ 0.35	$ 1.85	$ 0.42
Earnings Per Share (Textuals) [Abstract]
Convertible preferred shares									0	0	325,103
Weighted Average Limited Partnership and General Partnership Units Outstanding, Basic	324,364,000	315,513,000	314,255,000	312,011,000	309,120,000	308,884,000	307,954,000	306,248,000
Weighted Average Number Of Limited Partnership And General Partnership Unit Outstanding Diluted	327,108,000	318,773,000	317,648,000	315,230,000	312,731,000	312,844,000	312,199,000	306,248,000
OPERATING PARTNERSHIP
Numerator for net income per share - basic and diluted
(Loss) income from continuing operations									311,555,000	57,794,000	(103,108,000)
Net (income) loss attributable to Noncontrolling Interests - Partially Owned Properties									(844,000)	(832,000)	726,000
Premium on redemption of Preferred Shares									(5,152,000)	0	0
Discontinued operations, net									569,649,000	877,403,000	399,091,000
Net income available to Common Shares									$ 2.729	$ 2.984	$ 0.952
Net income per share - basic:
Income (loss) from continuing operations available to Common Shares									$ 0.932	$ 0.140	$ (0.393)
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share									$ 1.797	$ 2.844	$ 1.345
Net income available to Common Shares									$ 2.729	$ 2.984	$ 0.952
Net income per share - diluted:
Income (loss) from continuing operations available to Common Shares									$ 0.923	$ 0.138	$ (0.393)
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share									$ 1.782	$ 2.812	$ 1.345
Net income per share - diluted									$ 2.705	$ 2.950	$ 0.952
Earnings Per Share (Textuals) [Abstract]
Net (income) loss attributable to Noncontrolling Interests - Partially Owned Properties									$ (844,000)	$ (832,000)	$ 726,000
Weighted Average Limited Partnership and General Partnership Units Outstanding, Basic									316,554,000	308,062,000	296,527,000
Weighted Average Number Of Limited Partnership And General Partnership Unit Outstanding Diluted									319,766,000	312,065,000	296,527,000