Income per Common Share of the Trust (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Income from continuing operations net of noncontrolling interest	$ 30,951	$ 25,179
Discontinued operations net of noncontrolling interest	0	46,721
Net income available to common shareholders	$ 30,951	$ 71,900
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic	148,315	146,425
Dilutive shares for long-term compensation plans	716	670
Weighted Average Number of Shares Outstanding, Diluted	149,031	147,095
Common shares [Member]
Earnings Per Share, Basic [Abstract]
Income from Continuing Operations, Per Basic Share	$ 0.21	$ 0.17
Income from Discontinued Operations, Per Basic Share	$ 0.00	$ 0.32
Income per common share - basic	$ 0.21	$ 0.49
Earnings Per Share, Diluted [Abstract]
Income from Continuing Operations, Per Diluted Share	$ 0.21	$ 0.17
Income from Discontinued Operations, Per Diluted Share	$ 0.00	$ 0.32
Income per common share - diluted	$ 0.21	$ 0.49

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount of income (loss) from a disposal group, net of income tax, reported as a separate component of income before extraordinary items after deduction or consideration of the amount allocable to noncontrolling interests. Includes, 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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Per basic share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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