Organization and Ownership (Details)	Dec. 31, 2020 ft² property residential_unit building project tenant
Real Estate Properties [Line Items]
Rentable Square Feet	14,620,166
Stabilized office properties [Member]
Real Estate Properties [Line Items]
Number of buildings | building	117
Rentable Square Feet	14,620,166
Number of Tenants | tenant	447
Percentage Occupied	91.20%
Percentage Leased (unaudited)	94.30%
Stabilized residential properties [Member]
Real Estate Properties [Line Items]
Number of buildings | property	2
Percentage Occupied	72.00%
Number of residential units | property	808
In-process development projects - tenant improvement [Member]
Real Estate Properties [Line Items]
Number of buildings | property	3
Rentable Square Feet	1,080,000
In-process development projects - under construction [Member]
Real Estate Properties [Line Items]
Number of buildings | project	3
Rentable Square Feet	856,000
Number of residential units | residential_unit	193