Related Party Transactions (Details)	1 Months Ended							12 Months Ended					32 Months Ended
	Nov. 30, 2019 USD ($)	Aug. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) apartment	Feb. 28, 2019 USD ($)	Oct. 31, 2018 USD ($) apartment	May 31, 2018 USD ($) apartment	Mar. 31, 2017 USD ($) unit	Dec. 31, 2020 USD ($) unit	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($) investment	Dec. 31, 2020 USD ($)	Nov. 30, 2016 USD ($)
Related Party Transaction [Line Items]
Management and other fees from affiliates								$ 11,300,000	$ 13,800,000	$ 13,900,000
Revenues from development and redevelopment fees								1,700,000	4,300,000	4,800,000
Notes receivable								$ 195,104,000	134,365,000				$ 195,104,000
Number of units acquired | unit								2,020
Purchase price								$ 463,400,000	373,300,000
Debt assumed in connection with acquisition								0	143,006,000	45,804,000
Payments to acquire equity method investments								114,017,000	402,284,000	162,437,000
Co-investments								1,018,010,000	1,335,339,000				1,018,010,000
Encumbrance								643,550,000					643,550,000
Redeemed equity method investment										5,000,000.0	$ 5,000,000.0
Brio
Related Party Transaction [Line Items]
Number of units acquired | apartment			300
Purchase price			$ 164,900,000
Debt assumed in connection with acquisition			$ 98,700,000
Apartment Home Community in Ventura, California
Related Party Transaction [Line Items]
Number of units acquired | apartment						400
Annualized preferred return rate						10.25%
Preferred equity investment, commitment to fund						$ 26,500,000
Purchase commitment, funded amount													23,400,000
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
Related Party Bridge Loans on Property Acquired by Wesco V
Related Party Transaction [Line Items]
Notes receivable								0	85,713,000				0
Marcus and Millichamp Company TMMC Affiliate | Related Party Note Receivable, Secured, Bearing Interest at 9.5%, Due October 2019
Related Party Transaction [Line Items]
Notes receivable														$ 6,600,000
Affiliated Entity
Related Party Transaction [Line Items]
Due from Affiliates								4,700,000	4,400,000				$ 4,700,000
Affiliated Entity | Multifamily Development in Mountain View, California
Related Party Transaction [Line Items]
Payments to acquire equity method investments				$ 24,500,000
Annualized preferred return rate				11.00%
Affiliated Entity | Home Community Development in Burlingame, California
Related Party Transaction [Line Items]
Number of units acquired | apartment					268
Payments to acquire equity method investments					$ 18,600,000
Annualized preferred return rate					12.00%
Affiliated Entity | Related Party Bridge Loans on Property Acquired by Wesco V
Related Party Transaction [Line Items]
Notes receivable, related parties	$ 85,500,000	$ 89,000,000.0
Interest rate	1.30%	1.30%
Affiliated Entity | Related Party Bridge Loan on Property Acquired by Bex Iv
Related Party Transaction [Line Items]
Notes receivable, related parties		$ 44,400,000
Interest rate		3.25%
Limited Liability Company
Related Party Transaction [Line Items]
Payments to acquire equity method investments												$ 20,000,000.0
Number of equity method investments acquired during the period | investment												3
Cumulative dividend rate												9.50%
Disposition of Multi-family Properties | Marcus and Millichamp Company TMMC Affiliate
Related Party Transaction [Line Items]
Payments for brokerage fees								$ 200,000	$ 0	$ 0