Organization of The Parent Company and The Operating Partnership (Textual) (Details)	Mar. 31, 2016 ft² a property Real_Estate_Investments real_estate_venture Building Apartment_unit	Feb. 04, 2016 property
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	121
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	106
Rentable Square Feet | ft²	4,787,475
Industrial Properties [Member] | MAP Venture [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	6	20
Nine Real Estate Ventures [Member] | Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | Building	88
Number of unconsolidated investments in Real Estate Ventures | real_estate_venture	9
Rentable Square Feet | ft²	8,100,000
Mixed Use Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	9
Retail Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	1
Core Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	116
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	3
Redevelopment Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	1
Re-entitlement Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties	1
Undeveloped Land [Member] | Two Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | real_estate_venture	2
Acreage of land | a	4.3
Under Active Development Land [Member] | Three Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | real_estate_venture	3
Acreage of land | a	2.2
Residential Tower [Member] | One Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | real_estate_venture	1
Number of Property units | Apartment_unit	345
Apartment Complex [Member] | One Other Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | real_estate_venture	1
Number of Property units | Apartment_unit	398
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	99.10%
Net Rentable Square Feet | ft²	18,200,000
Area Owned by Company of Undeveloped Parcels of Land | a	292
Area of Additional Undeveloped Parcels of Land With Option to Purchase | a	50
Total Potential Development Capacity | ft²	6,400,000
Unconsolidated Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Unconsolidated Real Estate Ventures | Real_Estate_Investments	16
Unconsolidated Real Estate Ventures [Member] | Nine Real Estate Ventures [Member] | Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investments	9
Rentable Square Feet | ft²	8,100,000
Unconsolidated Real Estate Ventures [Member] | Undeveloped Land [Member] | Two Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investments	2
Acreage of land | a	4.3
Unconsolidated Real Estate Ventures [Member] | Under Active Development Land [Member] | Three Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investments	3
Acreage of land | a	2.2
Unconsolidated Real Estate Ventures [Member] | Residential Tower [Member] | One Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investments	1
Number of Property units	345
Unconsolidated Real Estate Ventures [Member] | Apartment Complex [Member] | One Other Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investments	1
Number of Property units	398
Wholly-owned Management Company Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet | ft²	29,300,000
Wholly-owned Management Company Subsidiaries [Member] | Partially Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet | ft²	11,100,000
Wholly-owned Management Company Subsidiaries [Member] | Wholly Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet | ft²	18,200,000
Wholly-owned Management Company Subsidiaries [Member] | Office and Industrial Properties [Member] | Partially Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet | ft²	11,100,000