Organization and Ownership (Details) - Dec. 31, 2019	building	property	ft²	Total	project	residential_unit	tenant
Real Estate Properties [Line Items]
Rentable Square Feet			13,475,795
Stabilized office properties [Member]
Real Estate Properties [Line Items]
Number of buildings	112	4
Rentable Square Feet			13,475,795
Number of Tenants | tenant							451
Percentage Occupied				94.60%
Percentage Leased (unaudited)				97.00%
Stabilized residential properties [Member]
Real Estate Properties [Line Items]
Number of buildings | building	1
Percentage Occupied				82.40%
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			846,000
In-process development projects - under construction [Member]
Real Estate Properties [Line Items]
Number of buildings | project					6
Rentable Square Feet			2,291,000
Completed residential development project [Member]
Real Estate Properties [Line Items]
Number of buildings | project					1
Rentable Units | residential_unit						237
Retail site [Member] | In-process development projects - under construction [Member]
Real Estate Properties [Line Items]
Number of residential units | residential_unit						564