Segment Information - Summary of Certain Balance Sheet Data by Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Segment Reporting Information
Real estate, at cost	$ 5,978,969	$ 6,000,631
Investments in unconsolidated real estate ventures	455,476	461,369
Total assets (1)	6,019,317	6,079,547
Operating Segments | Commercial Segment
Segment Reporting Information
Real estate, at cost	3,457,426	3,459,171
Investments in unconsolidated real estate ventures	321,741	327,798
Total assets (1)	3,416,231	3,430,509
Operating Segments | Multifamily
Segment Reporting Information
Real estate, at cost	2,114,399	2,036,131
Investments in unconsolidated real estate ventures	108,877	108,593
Total assets (1)	1,827,316	1,787,718
Other
Segment Reporting Information
Real estate, at cost	407,144	505,329
Investments in unconsolidated real estate ventures	24,858	24,978
Total assets (1)	$ 775,770	$ 861,320