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Organization of The Parent Company and The Operating Partnership (Details) |  |  |  | 9 Months Ended
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Sep. 30, 2011 | Mar. 31, 2011 Property | Sep. 30, 2011 Office Properties [Member] Property | Sep. 30, 2011 Industrial facilities [Member] Property | Sep. 30, 2011 Mixed-use properties [Member] Property | Sep. 30, 2011 Parent Company [Member] sqft | Sep. 30, 2011 Unconsolidated real estate ventures [Member] sqft Property | Sep. 30, 2011 Wholly-owned management company subsidiaries [Member] sqft | Sep. 30, 2011 Third Parties and Unconsolidated Real Estate Ventures [Member] sqft
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract] |  |  |  |  |  |  |  |  |
Ownership in the Operating Partnership | 93.20% |  |  |  |  |  |  |  |
Number of unconsolidated real estate ventures |  |  |  |  |  |  | 16 |  |
Total number of properties owned |  | 3 | 211 | 20 | 5 |  |  |  |
Net rentable square feet |  |  |  |  |  | 25,900,000 | 6,100,000 | 33,800,000 | 7,900,000

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- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + Details
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