Condensed Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues
Revenues from rental property	$ 226,709	$ 211,637	$ 447,054	$ 425,607
Management and other fee income	8,710	8,437	18,135	18,100
Total revenues	235,419	220,074	465,189	443,707
Operating expenses
Rent	2,932	3,807	6,201	7,101
Real estate taxes	29,632	28,141	59,175	57,562
Operating and maintenance	28,980	26,868	56,938	59,432
General and administrative expenses	30,973	29,612	65,404	59,358
Impairment charges			34,570	12,352
Depreciation and amortization	63,124	59,131	124,917	121,963
Total operating expenses	180,136	151,280	338,583	309,137
Operating income	55,283	68,794	126,606	134,570
Other income/(expense)
Mortgage and other financing income	1,985	1,940	3,992	3,769
Interest, dividends and other investment income	349	8,932	510	13,797
Other income/(expense), net	511	772	(3,077)	479
Interest expense	(57,387)	(55,601)	(114,881)	(110,941)
Income from other real estate investments	416	447	1,143	612
Income from continuing operations before income taxes, equity in income of joint ventures and equity in income from other real estate investments	1,157	25,284	14,293	42,286
Benefit/(provision) for income taxes, net	4,656	(5,640)	616	(9,893)
Equity in income of investment			79,246	30,169
Income from continuing operations	62,387	42,299	119,258	72,897
Discontinued operations
(Loss)/income from discontinued operating properties, net of tax	(4,285)	487	(6,283)	4,940
Impairment/loss on operating properties sold, net of tax	(1,037)	(5,496)	(8,741)	(8,689)
Gain on disposition of operating properties	11,263	4,025	23,242	4,188
Income/(loss) from discontinued operations	5,941	(984)	8,218	439
Gain on sale of operating properties, net of tax	4,059		4,059
Net income	72,387	41,315	131,535	73,336
Net income attributable to noncontrolling interests	(3,275)	(2,606)	(8,785)	(5,665)
Net income attributable to the Company	69,112	38,709	122,750	67,671
Preferred stock dividends	(20,841)	(14,841)	(36,415)	(29,681)
Net income available to the Company's common shareholders	48,271	23,868	86,335	37,990
Income from continuing operations:
-Basic (in Dollars per share)	$ 0.10	$ 0.06	$ 0.20	$ 0.09
-Diluted (in Dollars per share)	$ 0.10	$ 0.06	$ 0.20	$ 0.09
Net income:
-Basic (in Dollars per share)	$ 0.12	$ 0.06	$ 0.21	$ 0.09
-Diluted (in Dollars per share)	$ 0.12	$ 0.06	$ 0.21	$ 0.09
Weighted average shares:
-Basic (in Shares)	405,560	406,559	405,916	406,500
-Diluted (in Shares)	406,476	407,562	406,827	407,472
Amounts available to the Company's common shareholders:
Income from continuing operations, net of tax	42,381	24,970	80,399	37,778
Income/(loss) from discontinued operations	5,890	(1,102)	5,936	212
Net income	48,271	23,868	86,335	37,990
Equity In Income Of Joint Ventures, Net [Member]
Other income/(expense)
Equity in income of investment	42,500	17,824	79,246	30,169
Equity In Income From Other Real Estate Investments, Net [Member]
Other income/(expense)
Equity in income of investment	14,074	4,831	25,103	10,335
Segment, Continuing Operations [Member]
Operating expenses
Impairment charges	$ 24,495	$ 3,721	$ 25,948	$ 3,721