Organization and Basis of Presentation - Accumulated Other Comprehensive Loss - Partnership (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	$ 6,396,825
Balance at period end	6,436,028
Essex Portfolio, L.P. [Member] | Accumulated Other Comprehensive Loss, Net [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(15,229)
Cumulative effect upon adoption		$ (2,228)
Other comprehensive income before reclassification	18,610
Amounts reclassified from accumulated other comprehensive loss	(6,061)
Other comprehensive income	10,321
Balance at period end	(4,908)
Essex Portfolio, L.P. [Member] | Change in Fair Value and Amortization of Swap Settlements [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(17,417)
Cumulative effect upon adoption		0
Other comprehensive income before reclassification	18,697
Amounts reclassified from accumulated other comprehensive loss	(6,067)
Other comprehensive income	12,630
Balance at period end	(4,787)
Essex Portfolio, L.P. [Member] | Unrealized Gains/(Loss) on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	2,188
Cumulative effect upon adoption		$ (2,228)
Other comprehensive income before reclassification	(87)
Amounts reclassified from accumulated other comprehensive loss	6
Other comprehensive income	(2,309)
Balance at period end	$ (121)