Organization of The Parent Company and The Operating Partnership (Textual) (Details)	Jun. 30, 2016	Jun. 30, 2016 property	Jun. 30, 2016 ft²	Jun. 30, 2016 Real_Estate_Investment	Jun. 30, 2016 a	Jun. 30, 2016 Building	Jun. 30, 2016 Apartment_unit	Feb. 04, 2016 property
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		120
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		102
Rentable Square Feet			4,984,700
Mixed Use Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		9
Retail Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		1
Core Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		112
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		4
Redevelopment Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		2
One Real Estate Ventures [Member] | Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet			172,286
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment				1
Assets Held-for-sale [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		2
Unconsolidated 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_Investment				16
Unconsolidated Real Estate Ventures [Member] | Eight Real Estate Ventures [Member] | Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | Building						73
Unconsolidated Real Estate Ventures [Member] | Eight Real Estate Ventures [Member] | Office And Industrial Buildings [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment				8
Rentable Square Feet			7,900,000
Unconsolidated Real Estate Ventures [Member] | Two Real Estate Ventures [Member] | Undeveloped Land [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment				2
Acreage of land | a					4.3
Unconsolidated Real Estate Ventures [Member] | Three Real Estate Ventures [Member] | Under Active Development Land [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment				3
Acreage of land | a					2.2
Unconsolidated Real Estate Ventures [Member] | One Real Estate Ventures [Member] | Residential Tower [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment				1
Number of Property units		345					345
Unconsolidated Real Estate Ventures [Member] | One Other Real Estate Ventures [Member] | Apartment Complex [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment				1
Number of Property units		398					398
1000 Chesterbrook [Member] | One Real Estate Ventures [Member] | Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet			172,286
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment				1
Equity method investment percentage	50.00%
MAP Venture [Member] | Industrial Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property		6						20
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			18,100,000
Area Owned by Company of Undeveloped Parcels of Land | a					285
Area of Additional Undeveloped Parcels of Land With Option to Purchase | a					50
Total Potential Development Capacity			6,300,000
Wholly-owned Management Company Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet			29,200,000
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			11,200,000
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			18,000,000
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			11,200,000