Related Party Transactions (Details)	1 Months Ended								3 Months Ended		6 Months Ended		38 Months Ended
	Mar. 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Nov. 30, 2019 USD ($)	Jun. 30, 2019 USD ($) apartment	Feb. 28, 2019 USD ($)	Oct. 31, 2018 USD ($) apartment	May 31, 2018 USD ($) apartment	Mar. 31, 2017 USD ($) unit	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Related Party Transaction [Line Items]
Payments to acquire preferred equity investments											$ 160,719,000	$ 43,817,000
Preferred return rate		10.00%
Commitment to fund preferred equity investment		$ 20,000,000.0
Co-investments									$ 1,037,270,000		1,037,270,000		$ 1,037,270,000	$ 1,018,010,000
Membership Interest In Sage At Cupertino
Related Party Transaction [Line Items]
Number of units acquired | unit								230
Co-investments								$ 15,300,000
Investment interest acquired								40.50%
Contract price								$ 90,000,000.0
Encumbrance								$ 52,000,000.0
Affiliated Entity
Related Party Transaction [Line Items]
Management and other fees from affiliates									2,600,000	$ 2,600,000	4,800,000	5,700,000
Development and redevelopment fees									300,000	300,000	300,000	800,000
Short-term loans outstanding and due from affiliates									57,900,000		57,900,000		57,900,000	$ 4,700,000
Affiliated Entity | Related party bridge loan - Wesco I
Related Party Transaction [Line Items]
Notes receivable	$ 52,500,000								52,800,000		52,800,000		52,800,000
Interest rate	2.55%
Affiliated Entity | Related party bridge loan - Wesco V
Related Party Transaction [Line Items]
Notes receivable			$ 85,500,000
Interest rate			1.30%
Chairman and founder | Multifamily development community in La Mesa, CA
Related Party Transaction [Line Items]
Payments to acquire preferred equity investments					$ 24,500,000
Preferred return rate					11.00%
Chairman and founder | Apartment home community development development in Burlingame, CA
Related Party Transaction [Line Items]
Number of units acquired | apartment						268
Payments to acquire preferred equity investments						$ 18,600,000
Preferred return rate						12.00%
Chairman and founder | Marcus & Millichap Company (MMC)
Related Party Transaction [Line Items]
Brokerage commissions									$ 0	$ 0	$ 0	$ 200,000
Chairman and founder | Marcus & Millichap Company (MMC) | Brio, Walnut Creek, CA
Related Party Transaction [Line Items]
Number of units acquired | apartment				300
Payments to acquire real estate				$ 164,900,000
Debt assumed in connection with acquisition				$ 98,700,000
Chairman and founder | Marcus & Millichap Company (MMC) | Apartment home community in Ventura, CA
Related Party Transaction [Line Items]
Number of units acquired | apartment							400
Preferred return rate							10.25%
Commitment to fund preferred equity investment							$ 26,500,000
Commitment funded amount													$ 23,400,000