Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues
Revenues from rental properties	$ 884,782	$ 825,737	$ 786,940
Management and other fee income	37,522	35,320	39,866
Total revenues	922,304	861,057	826,806
Operating expenses
Rent	12,761	13,863	13,731
Real estate taxes	115,282	108,782	105,336
Operating and maintenance	118,787	114,101	108,357
General and administrative expenses	124,480	118,873	109,034
Provision for doubtful accounts	6,880	7,723	10,642
Impairment charges	59,569	32,763	39,121
Depreciation and amortization	249,493	231,712	217,205
Total operating expenses	664,794	608,131	596,966
Operating income	257,510	252,926	229,840
Other income/(expense)
Mortgage financing income	7,504	7,273	9,405
Interest, dividends and other investment income	2,170	16,567	21,229
Other expense, net	(7,971)	(4,680)	(4,459)
Interest expense	(227,595)	(223,526)	(223,032)
Early extinguishment of debt			(10,811)
Income from other real estate investments	2,451	3,824	3,653
Gain on sale of development properties		12,074	2,080
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	34,069	64,458	27,905
Provision for income taxes, net	(3,939)	(21,330)	(3,208)
Equity in income of equity method investments, net	112,896	63,467	55,705
Income from continuing operations	211,978	158,977	120,122
Discontinued operations
Income from discontinued operating properties, net of tax	3,084	23,021	43,366
Impairment/loss on operating properties sold, net of tax	(22,339)	(17,343)	(6,175)
Gain on disposition of operating properties, net of tax	83,253	17,327	1,961
Income from discontinued operations	63,998	23,005	39,152
Loss on transfer of operating properties, net			(57)
Gain on sale of operating properties, net of tax	4,299	108	2,434
Total net gain on transfer of operating properties, net	4,299	108	2,377
Net income	280,275	182,090	161,651
Net income attributable to noncontrolling interests	(14,202)	(13,039)	(18,783)
Net income attributable to the Company	266,073	169,051	142,868
Preferred stock redemption costs	(21,703)
Preferred stock dividends	(71,697)	(59,363)	(51,346)
Net income available to the Company's common shareholders	172,673	109,688	91,522
Income from continuing operations:
-Basic (in Dollars per share)	$ 0.27	$ 0.22	$ 0.14
-Diluted (in Dollars per share)	$ 0.27	$ 0.21	$ 0.14
Net income attributable to the Company:
-Basic (in Dollars per share)	$ 0.42	$ 0.27	$ 0.22
-Diluted (in Dollars per share)	$ 0.42	$ 0.27	$ 0.22
Weighted average shares:
-Basic (in Shares)	405,997	406,530	405,827
-Diluted (in Shares)	406,689	407,669	406,201
Amounts attributable to the Company's common shareholders:
Income from continuing operations, net of tax	110,406	88,067	57,658
Income from discontinued operations	62,267	21,621	33,864
Net income	172,673	109,688	91,522
Gains on change in control of interests	15,555	569
Joint Ventures [Member]
Other income/(expense)
Equity in income of equity method investments, net	112,896	63,467	34,579
Other Real Estate Investments [Member]
Other income/(expense)
Equity in income of equity method investments, net	53,397	51,813	60,846
Segment, Continuing Operations [Member]
Operating expenses
Impairment charges	$ 37,111	$ 13,077	$ 32,661