Earnings Per Share and Earnings Per Unit (Details 1) (USD $)	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Aug. 18, 2011
Numerator for net income per Unit basic and diluted
Income (loss) from continuing operations	$ 35,491,000	$ (295,000)	$ 47,908,000	$ (32,667,000)
Partially Owned Properties	(387,000)	188,000	(418,000)	623,000
Discontinued operations, net	77,486,000	30,121,000	779,888,000	130,438,000
Earnings Per Share (Textuals) [Abstract]
Convertible preferred shares	0	393,724	0	396,098
Unsecured Notes, face amount	650,000,000		650,000,000
Convertible Notes, outstanding	482,500,000		482,500,000		482,500,000
OPERATING PARTNERSHIP
Numerator for net income per Unit basic and diluted
Income (loss) from continuing operations	35,491,000	(295,000)	47,908,000	(32,667,000)
Partially Owned Properties	(387,000)	188,000	(418,000)	623,000
Allocation to Preference Units	(3,466,000)	(3,617,000)	(10,399,000)	(10,855,000)
Income (loss) from continuing operations available to Units	31,638,000	(3,724,000)	37,091,000	(42,899,000)
Discontinued operations, net	77,486,000	30,121,000	779,888,000	130,438,000
Numerator for net income per Unit - basic and diluted	109,124,000	26,397,000	816,979,000	87,539,000
Denominator for net income per Unit - basic and diluted
Denominator for net income per Unit- basic	308,884,000	296,348,000	307,705,000	295,572,000
Effect of dilutive securities:
Dilution for Units issuable upon assumed exercise/vesting of the company's long-term compensation award shares/units	3,960,000		4,203,000
Denominator for net income per Unit - diluted	312,844,000	296,348,000	311,908,000	295,572,000
Net income per Unit - basic	$ 0.35	$ 0.09	$ 2.65	$ 0.30
Net income per Unit - diluted	$ 0.35	$ 0.09	$ 2.62	$ 0.30
Net income per Unit - basic:
Income from continuing operations available to Units	$ 0.10	$ (0.01)	$ 0.12	$ (0.15)
Discontinued operations, net	$ 0.251	$ 0.102	$ 2.531	$ 0.441
Net income per Unit - basic	$ 0.35	$ 0.09	$ 2.65	$ 0.30
Net income per Unit - diluted
Income from continuing operations available to Units	$ 0.10	$ (0.01)	$ 0.12	$ (0.15)
Discontinued operations, net	$ 0.248	$ 0.102	$ 2.500	$ 0.441
Net income per Unit - diluted	$ 0.35	$ 0.09	$ 2.62	$ 0.30
Earnings Per Share (Textuals) [Abstract]
Convertible preferred shares	0	393,724	0	396,098
Unsecured Notes, face amount	650,000,000		650,000,000
Convertible Notes, outstanding	$ 482,500,000		$ 482,500,000

Amount of net (income) loss for the period allocated to noncontrolling partners in partially owned properties.

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Capital impact of aggregate cash stock and paid-in-kind dividends declared for preference units during the periods.

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Earnings Per Share.

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Effect of dilutive securities.

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The amount of income or loss from continuing operations, available to each outstanding limited partnership and general partnership unit in a publicly traded limited partnership or master limited partnership (MLP) during the reporting period.

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Net income loss per outstanding limited partnership and general partnership unit.

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The average number of units issued and outstanding that are used in calculating diluted earnings per unit determined based on the timing of issuance of units in the period.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

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The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses and taxes from ongoing operations before extraordinary items, and noncontrolling interest.

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This element represents the overall income (loss) from a disposal group that is classified as a component of the entity, net of income tax, reported as a separate component of income before extraordinary items before deduction or consideration of the amount which may be allocable to noncontrolling interests, if any. Includes the following (net of tax): income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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The amount of income (loss) from disposition of discontinued operations available to each limited partnership and general partnership unit during the reporting period, net of tax.

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Net income (loss) allocated to each outstanding limited partnership and general partnership unit.

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Weighted average number of limited partnership and general partnership units outstanding determined by relating the portion of time within a reporting period that limited partnership and general partnership units have been outstanding to the total time in that period. Includes, for example, the number of units distributed to unit holders whereby unit holders have the ability to elect to receive the unit holders' entire distribution in cash or units of equivalent value or there is a potential limitation on the total amount of cash that all unit holders can elect to receive in aggregate.

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