Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Computation of basic and diluted earnings per share
Numerator for basic and diluted earnings per share - net income (loss) attributable to common stockholders	$ 312,639	$ 148,969
Denominator for basic earnings per share - weighted average shares	362,534	355,076
Effect of dilutive securities:
Employee stock options	70	101
Non-vested restricted shares	397	253
Redeemable shares	1,651	621
Dilutive potential common shares	2,118	975
Denominator for diluted earnings per share - adjusted weighted average shares	364,652	356,051
Basic earnings per share	$ 0.86	$ 0.42
Diluted earnings per share	$ 0.86	$ 0.42

Computation of basic and diluted earnings per share.

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Incremental Common Shares Attributable to Employee stock options.

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Incremental Common Shares Attributable to Nonvested restricted shares.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of operating partnership units.

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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) for 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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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 sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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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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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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