Segment Information - Summary of Certain Balance Sheet Data by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting Information
Real estate, at cost	$ 6,026,135	$ 6,000,631
Investments in unconsolidated real estate ventures	486,052	461,369
Total assets (1)	6,008,978	6,079,547
Operating Segments | Commercial Segment
Segment Reporting Information
Real estate, at cost	3,494,929	3,459,171
Investments in unconsolidated real estate ventures	300,304	327,798
Total assets (1)	3,541,397	3,430,509
Operating Segments | Multifamily
Segment Reporting Information
Real estate, at cost	2,135,448	2,036,131
Investments in unconsolidated real estate ventures	110,369	108,593
Total assets (1)	1,779,416	1,787,718
Other
Segment Reporting Information
Real estate, at cost	395,758	505,329
Investments in unconsolidated real estate ventures	75,379	24,978
Total assets (1)	$ 688,165	$ 861,320