Organization and Basis of Presentation - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) community building investment partnership apartment project shares	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) community investment partnership shares	Jan. 01, 2020 USD ($)
Real Estate Properties [Line Items]
Apartment communities owned (in communities) | community	250
Apartment units owned (in apartments) | apartment	60,770
Ownership interest, number of commercial buildings (in commercial buildings) | building	1
Ownership interest, number of active development projects (in projects) | project	4
Ownership interest, number of unconsolidated joint venture projects (in projects) | project	2
Equity securities	$ 3,200		$ 3,600
Sales and maturities of marketable securities	200	$ 16,800
Marketable securities, realized gain (loss)	13	(100)
Gain (loss) on sale of equity securities	$ (8,696)	4,510
DownREIT limited partnerships consolidated by company (in partnerships) | partnership	17		17
Communities within DownREIT partnerships (in communities) | community	9		9
Number of previously consolidated co-investments considered VIE (in investments) | investment	6		6
Assets related to variable interest entities net of intercompany eliminations	$ 1,100,000		$ 1,000,000
Liabilities related to variable interest entities net of intercompany eliminations	348,900		364,300
Noncontrolling interest in variable interest entity	122,300		122,500
Fixed rate debt carrying amount	5,500,000		5,200,000
Fixed rate debt fair value	5,600,000		5,400,000
Variable rate debt, carrying amount	955,300		660,400
Variable rate debt fair value	949,200		655,800
Investments in mortgage back securities, fair value	75,100		72,700
Capitalized internal costs related to development and redevelopment projects	9,900	10,700
Redeemable noncontrolling interest	32,643		37,410
Mortgage backed securities
Real Estate Properties [Line Items]
Investments in mortgage backed securities, carrying value	75,045		$ 72,651
Interest And Other Income
Real Estate Properties [Line Items]
Gain (loss) on sale of equity securities	$ 8,700	4,500
Essex Portfolio, L.P.
Real Estate Properties [Line Items]
Operating Partnership units outstanding (in shares) | shares	2,296,043		2,301,653
Redemption value of operating partnership units outstanding	$ 505,700		$ 692,500
Gain (loss) on sale of equity securities	(8,696)	$ 4,510
Redeemable noncontrolling interest	$ 32,643		$ 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				$ (190)
ASU 2016-13
Real Estate Properties [Line Items]
Cumulative effect adjustment				(190)
ASU 2016-13 | Essex Portfolio, L.P.
Real Estate Properties [Line Items]
Cumulative effect adjustment				(190)
ASU 2016-13 | Distributions in Excess of Accumulated Earnings
Real Estate Properties [Line Items]
Cumulative effect adjustment				$ 200