Condensed Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues
Revenues from rental property	$ 222,961	$ 204,297	$ 660,502	$ 620,440
Management and other fee income	8,917	8,728	27,053	26,827
Total revenues	231,878	213,025	687,555	647,267
Operating expenses
Rent	3,270	3,455	9,457	10,545
Real estate taxes	29,917	27,827	87,606	83,985
Operating and maintenance	27,478	27,315	82,589	84,896
General and administrative expenses	29,957	30,846	95,317	90,188
Impairment charges			37,740	16,676
Depreciation and amortization	65,631	56,870	187,839	176,165
Total operating expenses	156,841	150,350	485,347	453,536
Operating income	75,037	62,675	202,208	193,731
Other income/(expense)
Mortgage and other financing income	2,092	1,959	6,083	5,728
Interest, dividends and other investment income	598	375	1,110	14,173
Other expense, net	(3,085)	(2,655)	(6,169)	(2,153)
Interest expense	(57,116)	(56,120)	(171,632)	(166,535)
Income from other real estate investments	545	2,449	1,688	3,062
Income from continuing operations before income taxes, equity in income of joint ventures and equity in income from other real estate investments	18,071	8,683	33,288	48,006
Provision for income taxes, net	(5,183)	(4,443)	(4,822)	(14,332)
Equity in income of investment			103,743	49,810
Income from continuing operations	47,625	48,669	167,549	118,607
Discontinued operations
Income/(loss) from discontinued operating properties, net of tax	734	5,678	(2,195)	13,521
Impairment/loss on operating properties sold, net of tax	(2,604)	(289)	(15,364)	(8,919)
Gain on disposition of operating properties, net of tax	11,329	4,535	34,571	8,722
Income from discontinued operations	9,459	9,924	17,012	13,324
Gain on sale of operating properties, net of tax			4,059
Net income	57,084	58,593	188,620	131,931
Net income attributable to noncontrolling interests	(2,143)	(3,612)	(10,928)	(9,277)
Net income attributable to the Company	54,941	54,981	177,692	122,654
Redemption costs	(6,213)		(6,213)
Preferred stock dividends	(21,622)	(14,841)	(58,037)	(44,522)
Net income available to the Company's common shareholders	27,106	40,140	113,442	78,132
Income from continuing operations:
-Basic (in Dollars per share)	$ 0.04	$ 0.07	$ 0.24	$ 0.16
-Diluted (in Dollars per share)	$ 0.04	$ 0.07	$ 0.24	$ 0.16
Net income:
-Basic (in Dollars per share)	$ 0.07	$ 0.10	$ 0.28	$ 0.19
-Diluted (in Dollars per share)	$ 0.07	$ 0.10	$ 0.28	$ 0.19
Weighted average shares:
-Basic (in Shares)	405,810	406,564	405,880	406,521
-Diluted (in Shares)	406,747	407,292	406,650	407,386
Amounts available to the Company's common shareholders:
Income from continuing operations, net of tax	16,761	30,191	97,795	65,010
Income from discontinued operations	10,345	9,949	15,647	13,122
Net income	27,106	40,140	113,442	78,132
Equity In Income Of Joint Ventures, Net [Member]
Other income/(expense)
Equity in income of investment	24,498	19,641	103,743	49,810
Equity In Income From Other Real Estate Investments, Net [Member]
Other income/(expense)
Equity in income of investment	10,239	24,788	35,340	35,123
Segment, Continuing Operations [Member]
Operating expenses
Impairment charges	$ 588	$ 4,037	$ 22,539	$ 7,757