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)	Jun. 30, 2019 ft² property
Real Estate Properties [Line Items]
Number of Properties | property	96
Rentable Square Feet | ft²	16,922,019
Office Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	88
Rentable Square Feet | ft²	15,719,636
Mixed-use Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	3
Rentable Square Feet | ft²	641,741
Retail Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	1
Rentable Square Feet | ft²	17,884
Core Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	92
Rentable Square Feet | ft²	16,379,261
Development Projects [Member]
Real Estate Properties [Line Items]
Number of Properties | property	1
Rentable Square Feet | ft²	204,108
Redevelopment Projects [Member]
Real Estate Properties [Line Items]
Number of Properties | property	3
Rentable Square Feet | ft²	338,650