Condensed Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues
Revenues from rental properties	$ 237,079	$ 217,809	$ 467,371	$ 429,892
Management and other fee income	9,049	8,710	17,442	18,136
Total revenues	246,128	226,519	484,813	448,028
Operating expenses
Rent	3,380	2,924	6,705	6,187
Real estate taxes	28,858	27,985	58,306	55,592
Operating and maintenance	31,445	26,756	59,567	52,413
General and administrative expenses	31,420	30,908	65,535	65,314
Provision for doubtful accounts	3,266	2,551	5,199	5,624
Impairment charges			81,546	34,570
Depreciation and amortization	63,409	59,731	125,136	118,299
Total operating expenses	197,144	150,947	356,212	303,754
Operating income	48,984	75,572	128,601	144,274
Other income/(expense)
Mortgage financing income	1,430	1,985	2,416	3,991
Interest, dividends and other investment income	6,500	350	9,163	512
Other (expense)/income, net	(2,526)	538	(6,002)	(3,058)
Interest expense	(55,423)	(56,776)	(108,970)	(113,757)
Income from other real estate investments	555	416	958	1,143
Income/(loss) from continuing operations before income taxes, equity in income of joint ventures, gain/(loss) on change in control of interests and equity in income from other real estate investments	(480)	22,085	26,166	33,105
Benefit/(provision) for income taxes, net	11,830	(3,302)	(3,937)	(8,089)
Equity in income of investment	59,500	30,400	83,616	65,090
Income from continuing operations	77,595	75,356	146,919	129,363
Discontinued operations
Income/(loss) from discontinued operating properties, net of tax	1,652	(180)	2,631	1,906
Impairment/loss on operating properties sold, net of tax	(27,844)	(18,111)	(30,675)	(27,035)
Gain on disposition of operating properties	1,869	11,263	4,365	23,242
Loss from discontinued operations	(24,323)	(7,028)	(23,679)	(1,887)
Gain on sale of operating properties, net of tax		4,059	540	4,059
Net income	53,272	72,387	123,780	131,535
Net income attributable to noncontrolling interests	(2,133)	(3,275)	(4,871)	(8,785)
Net income attributable to the Company	51,139	69,112	118,909	122,750
Preferred stock dividends	(14,573)	(20,841)	(29,147)	(36,415)
Net income available to the Company's common shareholders	36,566	48,271	89,762	86,335
Income from continuing operations:
-Basic (in Dollars per share)	$ 0.15	$ 0.14	$ 0.28	$ 0.22
-Diluted (in Dollars per share)	$ 0.15	$ 0.14	$ 0.28	$ 0.22
Net income attributable to the Company:
-Basic (in Dollars per share)	$ 0.09	$ 0.12	$ 0.22	$ 0.21
-Diluted (in Dollars per share)	$ 0.09	$ 0.12	$ 0.22	$ 0.21
Weighted average shares:
-Basic (in Shares)	407,640	405,560	407,154	405,916
-Diluted (in Shares)	408,831	406,476	408,163	406,827
Amounts attributable to the Company's common shareholders:
Income from continuing operations	60,889	55,394	113,458	90,615
Income from discontinued operations	(24,323)	(7,123)	(23,696)	(4,280)
Gain/(loss) on change in control of interests, net	(1,459)	12,147	21,711	14,156
Equity In Income Of Joint Ventures, Net [Member]
Other income/(expense)
Equity in income of investment	59,504	30,352	83,616	65,090
Equity In Income From Other Real Estate Investments, Net [Member]
Other income/(expense)
Equity in income of investment	8,200	14,074	19,363	25,101
Continuing Operations [Member]
Operating expenses
Impairment charges	$ 35,366	$ 92	$ 35,764	$ 325