Organization, Ownership and Basis of Presentation (Details) - Sep. 30, 2018	ft²	Total	tenant	building	number_of_residential_units	project	property
Stabilized office properties [Member]
Real Estate Properties [Line Items]
Number of Buildings				104			4
Rentable Square Feet (unaudited)	13,891,493
Number of Tenants | tenant			524
Percentage Occupied (unaudited)		93.50%
Percentage Leased (unaudited)		96.60%
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