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Organization of The Parent Company and The Operating Partnership (Details)	Jun. 30, 2011
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Ownership in the Operating Partnership	93.20%
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Total number of properties owned	209
Industrial facilities [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Total number of properties owned	20
Mixed-use properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Total number of properties owned	6
Mixed-use properties [Member] | Unconsolidated real estate ventures [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	25,700,000
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	25,700,000
Unconsolidated real estate ventures [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of unconsolidated real estate ventures	16
Net rentable square feet	6,100,000
Wholly-owned management company subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	33,700,000
Third Parties and Unconsolidated Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	8,000,000

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Net Rentable Space.

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Number of properties owned.

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Organization of The Parent Company and The Operating Partnership.

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The consolidating entity's interest in net assets of the subsidiary, expressed as a percentage.

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