Organization and Basis of Presentation - Accumulated Other Comprehensive Loss - Partnership (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 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	6,492,159
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	8,230
Amounts reclassified from accumulated other comprehensive loss	(2,054)
Other comprehensive income	3,948
Balance at period end	(11,281)
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	8,307
Amounts reclassified from accumulated other comprehensive loss	(2,053)
Other comprehensive income	6,254
Balance at period end	(11,163)
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	(77)
Amounts reclassified from accumulated other comprehensive loss	(1)
Other comprehensive income	(2,306)
Balance at period end	$ (118)