Commitments, Contingencies and Guarantees - Narrative (Details) ft² in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($) ft² apartment building property	Dec. 31, 2020 USD ($)
Other Commitments [Line Items]
Number of buildings containing asbestos | building	32
Principal balance	$ 5,002,123	$ 4,777,512
Partnership X | Floating rate term loan
Other Commitments [Line Items]
Principal balance	$ 104,800
Maturity date	Mar. 01, 2023
Number of properties secured by debt | property	2
Partnership X | Floating rate term loan | LIBOR
Other Commitments [Line Items]
Debt instrument, basis spread on variable rate	1.40%
Development Projects
Other Commitments [Line Items]
Aggregate remaining contractual commitment	$ 136,800
Development Projects | California
Other Commitments [Line Items]
Number of apartments under construction | apartment	376
Development Projects | Hawaii
Other Commitments [Line Items]
Number of apartments under construction | apartment	493
Retail square footage (sq ft) | ft²	490
Repositionings, Capital Expenditure Projects, and Tenant Improvements
Other Commitments [Line Items]
Aggregate remaining contractual commitment	$ 20,900