Organization of The Parent Company and The Operating Partnership - Summary of Core Portfolio of Operating Properties and Excludes Development, Redevelopment and Held for Sale (Details)	Sep. 30, 2020 ft² property
Real Estate Properties [Line Items]
Number of properties | property	92
Net rentable area (in square feet) | ft²	14,691,346
Office properties
Real Estate Properties [Line Items]
Number of properties | property	84
Net rentable area (in square feet) | ft²	13,641,289
Mixed-use properties
Real Estate Properties [Line Items]
Number of properties | property	5
Net rentable area (in square feet) | ft²	780,184
Core Properties
Real Estate Properties [Line Items]
Number of properties | property	89
Net rentable area (in square feet) | ft²	14,421,473
Development property
Real Estate Properties [Line Items]
Number of properties | property	1
Net rentable area (in square feet) | ft²	205,803
Redevelopment properties
Real Estate Properties [Line Items]
Number of properties | property	2
Net rentable area (in square feet) | ft²	64,070