Real Estate Investments Real Estate Investments - Acquisitions And Sales Of Real Estate (Details) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) unit	Jan. 31, 2017 USD ($)	Mar. 31, 2017 USD ($) unit	Dec. 31, 2017 USD ($) community unit	Dec. 31, 2016 USD ($) community unit	Dec. 31, 2010
Schedule of Equity Method Investments [Line Items]
Number of units acquired | unit				1,328
Purchase Price				$ 273,000
Limited partnership interest in partnership investments						3.00%
Co-investments				1,155,984	$ 1,161,275
Land and Land Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Purchase Price				169,500
Building and Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Purchase Price				365,700
Prepaid Expenses and Other Assets [Member]
Schedule of Equity Method Investments [Line Items]
Purchase Price				$ 3,200
Membership Interest In Palm Valley [Member]
Schedule of Equity Method Investments [Line Items]
Number of units acquired | unit			1,098
Purchase Price		$ 183,000	$ 183,000
Essex Ownership Percentage	100.00%		100.00%
Limited partnership interest in partnership investments		50.00%		50.00%
Co-investments		$ 183,000
Encumberance of mortgage debt					$ 220,000
Membership Interest In Sage At Cupertino [Member]
Schedule of Equity Method Investments [Line Items]
Number of units acquired | unit	230		230
Purchase Price	$ 90,000		$ 90,000
Essex Ownership Percentage	40.50%		40.50%
Co-investments	$ 15,300		$ 15,300
Encumberance of mortgage debt	$ 52,000		$ 52,000
Apartment Building [Member]
Schedule of Equity Method Investments [Line Items]
Number of communities acquired | community				2	4
Number of units acquired | unit				1,328	753
Purchase Price				$ 273,000	$ 333,700