Related Party Transactions (Details)	1 Months Ended								8 Months Ended	12 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	Nov. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) unit	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) unit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($) investment	Nov. 30, 2016 USD ($)
Related Party Transaction [Line Items]
Management and other fees from affiliates										$ 13,800,000	$ 13,900,000	$ 12,600,000
Revenues from development and redevelopment fees										4,300,000	4,800,000	3,000,000.0
Notes receivable									$ 71,895,000	$ 134,365,000	71,895,000
Number of units acquired | unit										849
Purchase price										$ 373,300,000	35,400,000
Debt assumed in connection with acquisition										143,006,000	45,804,000	51,882,000
Payments to acquire equity method investments										402,284,000	162,437,000	293,363,000
Co-investments									1,300,140,000	1,335,339,000	1,300,140,000
Encumbrance										990,667,000
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									22,500,000
Membership Interest in Sage at Cupertino
Related Party Transaction [Line Items]
Number of units acquired | unit								230
Co-investments								$ 15,300,000
Equity method investment, ownership percentage								40.50%
Contract price								$ 90,000,000.0
Encumbrance								$ 52,000,000.0
Notes and Other Receivables from Affiliates
Related Party Transaction [Line Items]
Notes receivable									4,500,000	4,400,000	4,500,000
Related Party Bridge Loan on Property Acquired by Bex Iv
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 | 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%
Affiliated Entity | Secured Note Receivable, 3.5% Interest Rate, Due March 9, 2018 | BEX III
Related Party Transaction [Line Items]
Notes receivable, related parties							$ 29,500,000
Interest rate							3.50%
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										$ 0	$ 0	$ 0