Organization of The Parent Company and The Operating Partnership (Details)	Dec. 31, 2013 acre
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Area of undeveloped parcels of land (in acres) owned by a Real Estate Venture	3.8
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Ownership in the Operating Partnership	98.80%
Net rentable square feet	24,800,000
Area Owned by Company of Undeveloped Parcels Of Land	432
Area of additional undeveloped parcels of land with option to purchase	51
Total potential development capacity	6,800,000
Unconsolidated real estate ventures [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of unconsolidated real estate ventures	17
Net rentable square feet	5,700,000
Wholly-owned management company subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	32,700,000
Third Parties and Unconsolidated Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	7,900,000
Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Ownership in the Operating Partnership	100.00%
Total Properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	204
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	176
Industrial facilities [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	19
Mixed-use properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	5
Development Property [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	1
Redevelopment Property [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	2
Re-entitlement Property [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	1