Real Estate Investments - Acquisitions (Details)	1 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($) community apartment	Dec. 31, 2019 USD ($) unit	Dec. 31, 2020 USD ($) unit	Dec. 31, 2019 USD ($) community apartment	Dec. 31, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of units acquired | unit			2,020
Purchase Price			$ 463,400,000	$ 373,300,000
Gain on remeasurement of co-investment			234,694,000	31,535,000	$ 1,253,000
Investment in real estate			15,061,745,000
Encumbrance			643,550,000
CPPIB Interest
Schedule of Equity Method Investments [Line Items]
Investment interest acquired	45.00%
Value of property held by acquired investment	$ 1,000,000,000.0
Gain on remeasurement of co-investment	234,700,000
Promote income	$ 6,500,000
Land and Land Improvements
Schedule of Equity Method Investments [Line Items]
Purchase Price			189,000,000.0
Building and Improvements
Schedule of Equity Method Investments [Line Items]
Purchase Price			846,000,000.0
Prepaid Expenses and Other Assets
Schedule of Equity Method Investments [Line Items]
Purchase Price			$ 10,000,000.0
Hidden Valley
Schedule of Equity Method Investments [Line Items]
Purchase Price		$ 24,200,000
Limited partnership interest		25.00%
Investment in real estate		$ 97,000,000.0		97,000,000.0
Encumbrance		$ 29,700,000		$ 29,700,000
Apartment Building
Schedule of Equity Method Investments [Line Items]
Number of communities held by acquired investment | community				4
Number of units held by acquired investment | apartment				849
Apartment Building | CPPIB Interest
Schedule of Equity Method Investments [Line Items]
Number of units acquired | unit			2,020
Essex Ownership Percentage			100.00%
Purchase Price			$ 463,400,000
Number of communities held by acquired investment | community	6
Number of units held by acquired investment | apartment	2,020
Apartment Building | Hidden Valley
Schedule of Equity Method Investments [Line Items]
Number of units acquired | unit		324