Organization of the Parent Company and The Operating Partnership (Details)	Mar. 31, 2014 Real_Estate_Investments sqft	Mar. 13, 2013 sqft
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	98.90%
Net rentable square feet	24,900,000
Area Owned by Company of Undeveloped Parcels Of Land	450
Area Of Additional Undeveloped Parcels Of Land With Option to Purchase	50
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	5,700,000	6,400,000
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	32,800,000
Third Parties and Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet	7,900,000
Total Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	205
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	175
Industrial Facilities [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	20
Mixed Use Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	5
Core Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	200
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	2
Redevelopment Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	2
Re-entitlement Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Real Estate Properties	1