Organization of the Parent Company and The Operating Partnership Organization of the Parent Company and The Operating Partnership (Details)	Jun. 30, 2013
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	98.80%
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet	24,200,000
Area Owned By Company Of Undeveloped Parcels Of Land	435
Area Of Additional Undeveloped Parcels Of Land With Option to Purchase	51
Total potential development capacity	6,200,000
Unconsolidated Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet	6,200,000
Number Of Unconsolidated Real Estate Ventures	17
Wholly-owned Management Company Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet	30,800,000
Third Parties and Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet	6,600,000
Total Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	210
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	182
Industrial Facilities [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	19
Mixed Use Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	5
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	1
Redevelopment Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	2
Re-entitlement Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	1