Organization, Ownership and Basis of Presentation (Details) - Jun. 30, 2018	ft²	Total	project	tenant	building	property	number_of_residential_units
Stabilized office properties [Member]
Real Estate Properties [Line Items]
Number of Buildings					104	4
Rentable Square Feet (unaudited)	13,881,509
Number of Tenants | tenant				519
Percentage Occupied (unaudited)		94.00%
Percentage Leased (unaudited)		96.80%
Stabilized residential properties [Member]
Real Estate Properties [Line Items]
Number of Buildings | building					1
Percentage Occupied (unaudited)		83.30%
Number of Units | building					200
In-process development projects - tenant improvement [Member]
Real Estate Properties [Line Items]
Number of Buildings | project			2
Rentable Square Feet (unaudited)	1,150,000
In-process development projects - under construction [Member]
Real Estate Properties [Line Items]
Number of Buildings | project			3
Rentable Square Feet (unaudited)	956,000
Number of residential units | number_of_residential_units							608
Retail site [Member] | In-process development projects - under construction [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)	120,000
Retail site [Member] | Production, Distribution and Repair (PDR) [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)	86,000