Background (Details)	Jun. 30, 2011	Dec. 31, 2010
Background
Number of properties in asset base	171
Rentable square feet, operating properties (in square feet)	12,672,852	12,500,000
Rentable square feet, redevelopment properties (in square feet)	782,258	755,463
Rentable square feet, development properties (in square feet)	690,139	475,818
Total	14,145,249

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The amount of rentable square feet related to real estate property.

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The amount of rentable square feet related to real estate operating properties.

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The amount of rentable square feet related to a real estate property undergoing active redevelopment.

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The amount of rentable square feet related to a real estate property undergoing active ground-up development.

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The number of real estate properties owned as of the balance sheet date.

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