Organization and Basis of Presentation - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) community building investment partnership apartment project shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) community building investment partnership apartment project shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) community investment partnership shares	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Real Estate Properties [Line Items]
Apartment communities owned (in communities) | community	248		248
Apartment units owned (in apartments) | apartment	60,341		60,341
Ownership interest, number of commercial buildings (in commercial buildings) | building	1		1
Ownership interest, number of active development projects (in projects) | project	4		4
Ownership interest, number of unconsolidated joint venture projects (in projects) | project	3		3
Accounting standards update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member		us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Cumulative effect adjustment	$ 6,352,881	$ 6,345,116	$ 6,352,881	$ 6,345,116	$ 6,403,504	$ 6,417,949	$ 6,317,195	$ 6,393,844
Equity securities	2,700		2,700		$ 3,600
Sales and maturities of marketable securities	4,100	33,400	4,300	50,200
Marketable securities, realized gain (loss)	$ 46	600	33	500
Gain (loss) on sale of equity securities			$ (1,073)	4,454
DownREIT limited partnerships consolidated by company (in partnerships) | partnership	17		17		17
Communities within DownREIT partnerships (in communities) | community	9		9		9
Number of previously consolidated co-investments considered VIE (in investments) | investment	5		5		6
Assets related to variable interest entities net of intercompany eliminations	$ 900,000		$ 900,000		$ 1,000,000
Liabilities related to variable interest entities net of intercompany eliminations	327,700		327,700		364,300
Noncontrolling interest in variable interest entity	121,500		121,500		122,500
Fixed rate debt carrying amount	5,500,000		5,500,000		5,200,000
Fixed rate debt fair value	6,000,000		6,000,000		5,400,000
Variable rate debt, carrying amount	805,100		805,100		660,400
Variable rate debt fair value	799,800		799,800		655,800
Investments in mortgage back securities, fair value	77,600		77,600		72,700
Capitalized internal costs related to development and redevelopment projects	8,900	10,400	18,800	21,100
Redeemable noncontrolling interest	33,241		33,241		37,410
Mortgage backed securities
Real Estate Properties [Line Items]
Investments in mortgage backed securities, carrying value	77,511		77,511		$ 72,651
Interest And Other Income
Real Estate Properties [Line Items]
Gain (loss) on sale of equity securities	$ 7,600	(56)	$ (1,100)	$ 4,500
Essex Portfolio, L.P.
Real Estate Properties [Line Items]
Operating Partnership units outstanding (in shares) | shares	2,295,510		2,295,510		2,301,653
Redemption value of operating partnership units outstanding	$ 526,100		$ 526,100		$ 692,500
Accounting standards update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member		us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Gain (loss) on sale of equity securities			$ (1,073)	$ 4,454
Redeemable noncontrolling interest	$ 33,241		$ 33,241		$ 37,410
Partnership Interest
Real Estate Properties [Line Items]
Ownership interest in partnership			96.60%		96.60%
Distributions in Excess of Accumulated Earnings
Real Estate Properties [Line Items]
Cumulative effect adjustment	$ (760,028)	$ (857,994)	$ (760,028)	$ (857,994)	$ (887,619)	$ (708,697)	$ (822,087)	$ (812,796)
Cumulative Effect, Period Of Adoption, Adjusted Balance | Distributions in Excess of Accumulated Earnings
Real Estate Properties [Line Items]
Cumulative effect adjustment					$ 200