Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues
Revenues from rental properties	$ 910,356	$ 836,881	$ 779,156
Management and other fee income	36,317	37,522	35,321
Total revenues	946,673	874,403	814,477
Operating expenses
Rent	13,347	12,745	13,847
Real estate taxes	117,563	110,747	104,451
Operating and maintenance	115,151	107,204	102,538
General and administrative expenses	127,913	123,925	118,559
Provision for doubtful accounts	8,256	6,022	5,965
Impairment charges	190,218	59,569	32,763
Depreciation and amortization	247,537	236,923	218,260
Total operating expenses	721,171	607,855	576,697
Operating income	225,502	266,548	237,780
Other income/(expense)
Mortgage financing income	4,304	7,504	7,273
Interest, dividends and other investment income	16,999	2,041	15,796
Other expense, net	(533)	(7,687)	(4,010)
Interest expense	(213,911)	(225,710)	(221,678)
Income from other real estate investments	2,306	2,451	4,121
Gain on sale of development properties			12,074
Income from continuing operations before income taxes, equity in income of joint ventures, gain on change in control of interests and equity in income from other real estate investments	34,667	45,147	51,356
Provision for income taxes, net	(34,520)	(16,922)	(25,789)
Equity in income of equity method investments, net	208,689	112,896	63,467
Income from continuing operations	261,683	210,073	141,416
Discontinued operations
Income from discontinued operating properties, net of tax	18,224	21,082	40,582
Impairment/loss on operating properties sold, net of tax	(83,900)	(38,432)	(17,343)
Gain on disposition of operating properties, net of tax	43,914	83,253	17,327
(Loss)/income from discontinued operations	(21,762)	65,903	40,566
Gain on sale of operating properties, net of tax	1,432	4,299	108
Net income	241,353	280,275	182,090
Net income attributable to noncontrolling interests	(5,072)	(14,202)	(13,039)
Net income attributable to the Company	236,281	266,073	169,051
Preferred stock redemption costs		(21,703)
Preferred dividends	(58,294)	(71,697)	(59,363)
Net income available to the Company's common shareholders	177,987	172,673	109,688
Income from continuing operations:
-Basic (in Dollars per share)	$ 0.47	$ 0.27	$ 0.18
-Diluted (in Dollars per share)	$ 0.47	$ 0.27	$ 0.18
Net income attributable to the Company:
-Basic (in Dollars per share)	$ 0.43	$ 0.42	$ 0.27
-Diluted (in Dollars per share)	$ 0.43	$ 0.42	$ 0.27
Weighted average shares:
-Basic (in Shares)	407,631	405,997	406,530
-Diluted (in Shares)	408,614	406,689	407,669
Amounts attributable to the Company's common shareholders:
Income from continuing operations	191,448	109,903	71,921
Income/(loss) from discontinued operations	(13,461)	62,770	37,767
Gain on change in control of interests, net	21,711	15,555	569
Joint Ventures [Member]
Other income/(expense)
Equity in income of equity method investments, net	208,689	112,896	63,467
Other Real Estate Investments [Member]
Other income/(expense)
Equity in income of equity method investments, net	31,136	53,397	51,813
Development Properties [Member]
Other income/(expense)
Gain on sale of development properties			12,074
Continuing Operations [Member]
Operating expenses
Impairment charges	$ 91,404	$ 10,289	$ 13,077