Acquisitions of Real Estate Property (Details 5) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Business Combinations [Abstract]
Revenues	$ 2,256,319	$ 2,178,897
Income from continuing operations attributable to common stockholders	$ 583,446	$ 321,637
Income from continuing operations attributable to common stockholders, Basic (in dollars per share)	$ 2.03	$ 1.14
Income from continuing operations attributable to common stockholders, Diluted (in dollars per share)	$ 2.02	$ 1.14
Basic (in shares)	286,856	281,333
Diluted (in shares)	289,193	282,382

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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-Publisher FASB

-Name Accounting Standards Codification

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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