Related Party Transactions (Details)	1 Months Ended						8 Months Ended	12 Months Ended
	Nov. 30, 2018	Oct. 31, 2018 USD ($) apartment	May 31, 2018 USD ($) apartment	Nov. 30, 2017 USD ($)	Aug. 31, 2017 USD ($)	Mar. 31, 2017 USD ($) unit	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) unit	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) investment	Nov. 30, 2016 USD ($)
Related Party Transaction [Line Items]
Management and other fees from affiliates								$ 13,900,000	$ 12,600,000	$ 12,400,000
Revenues from development and redevelopment fees								4,800,000	3,000,000	4,200,000
Notes receivable							$ 71,895,000	71,895,000	100,926,000
Payments to acquire equity method investments								$ 162,437,000	293,363,000	183,989,000
Number of units acquired | unit								166
Annualized preferred return rate	9.90%
Co-investments							1,300,140,000	$ 1,300,140,000	1,155,984,000
Encumbrance							1,806,626,000	1,806,626,000
Redeemed equity method investment									5,000,000
Apartment Home Community In Ventura, California [Member]
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							21,000,000
Membership Interest In Sage At Cupertino [Member]
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
Encumbrance						$ 52,000,000
Notes And Other Receivables From Affiliates [Member]
Related Party Transaction [Line Items]
Notes receivable							4,500,000	4,500,000	5,100,000
Related party note receivable, secured, bearing interest at 9.5%, due October 2019 [Member]
Related Party Transaction [Line Items]
Notes receivable							6,618,000	6,618,000	6,656,000
Secured Note Receivable, 3.5% Interest Rate, Due December 16, 2017 [Member]
Related Party Transaction [Line Items]
Notes receivable							0	0	29,500,000
Marcus and Millichamp Company TMMC Affiliate [Member] | Related party note receivable, secured, bearing interest at 9.5%, due October 2019 [Member]
Related Party Transaction [Line Items]
Notes receivable												$ 6,600,000
Marcus and Millichamp Company TMMC Affiliate [Member] | Disposition Of Multi-family Properties [Member]
Related Party Transaction [Line Items]
Payments for brokerage fees								0	0	$ 1,100,000
Limited Liability Company [Member]
Related Party Transaction [Line Items]
Payments to acquire equity method investments											$ 20,000,000
Number of equity method investments acquired during the period | investment											3
Cumulative dividend rate											9.50%
Limited Liability Company [Member] | Related party note receivable, secured, bearing interest at 9.5%, due October 2019 [Member] | Marcus and Millichamp Company TMMC Affiliate [Member]
Related Party Transaction [Line Items]
Notes receivable, related parties							6,600,000	6,600,000	$ 6,700,000
Affiliated Entity [Member] | Home Community Development in Burlingame, California [Member]
Related Party Transaction [Line Items]
Payments to acquire equity method investments		$ 18,600,000
Number of units acquired | apartment		268
Annualized preferred return rate		12.00%
Affiliated Entity [Member] | Secured Note Receivable, 3.5% Interest Rate, Due December 16, 2017 [Member] | Wesco V Property [Member]
Related Party Transaction [Line Items]
Notes receivable, related parties					$ 55,000,000
Notes receivable, related party, interest rate					3.50%
Affiliated Entity [Member] | Secured Note Receivable, 3.5% Interest Rate, Due March 9, 2018 [Member] | BEX III [Member]
Related Party Transaction [Line Items]
Notes receivable							$ 0	$ 0
Notes receivable, related parties				$ 29,500,000
Notes receivable, related party, interest rate				3.50%