Condensed Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues
Revenues from rental properties	$ 232,785	$ 214,564
Management and other fee income	8,393	9,425
Total revenues	241,178	223,989
Operating expenses
Rent	3,325	3,263
Real estate taxes	29,855	28,152
Operating and maintenance	28,849	26,415
General and administrative expenses	34,119	34,414
Provision for doubtful accounts	1,960	3,097
Impairment charges	3,229	9,563
Depreciation and amortization	62,738	59,556
Total operating expenses	164,044	155,130
Operating income	77,134	68,859
Other income/(expense)
Mortgage financing income	986	2,007
Interest, dividends and other investment income	2,663	164
Other expense, net	(3,485)	(3,597)
Interest expense	(53,624)	(57,283)
Income from other real estate investments	403	727
Income from continuing operations before income taxes, equity in income of joint ventures, gains on change in control of interests and equity in income from other real estate investments	24,077	10,877
Provision for income taxes, net	(15,133)	(4,054)
Equity in income of investment	24,111	34,738
Income from continuing operations	67,388	54,596
Discontinued operations
Income from discontinued operating properties, net of tax	115	1,497
Impairment/loss on operating properties sold, net of tax	(31)	(8,924)
Gain on disposition of operating properties	2,496	11,979
Income from discontinued operations	2,580	4,552
Gain on sale of operating properties, net of tax	540
Net income	70,508	59,148
Net income attributable to noncontrolling interests	(2,738)	(5,510)
Net income attributable to the Company	67,770	53,638
Preferred stock dividends	(14,573)	(15,574)
Net income available to the Company's common shareholders	53,197	38,064
Income from continuing operations:
-Basic (in Dollars per share)	$ 0.12	$ 0.09
-Diluted (in Dollars per share)	$ 0.12	$ 0.09
Net income attributable to the Company:
-Basic (in Dollars per share)	$ 0.13	$ 0.09
-Diluted (in Dollars per share)	$ 0.13	$ 0.09
Weighted average shares:
-Basic (in Shares)	406,662	406,272
-Diluted (in Shares)	407,666	407,279
Amounts attributable to the Company's common shareholders:
Income from continuing operations	50,605	35,754
Income from discontinued operations	2,592	2,310
Net income	53,197	38,064
Gains on change in control of interests	23,170	2,008
Equity In Income Of Joint Ventures, Net [Member]
Other income/(expense)
Equity in income of investment	24,111	34,738
Equity In Income From Other Real Estate Investments, Net [Member]
Other income/(expense)
Equity in income of investment	11,163	11,027
Segment, Continuing Operations [Member]
Operating expenses
Impairment charges	$ 3,198	$ 233