Organization and Basis of Presentation - Accumulated Other Comprehensive Loss - Partnership (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	$ 6,292,237
Balance at period end	6,383,894
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	(29,348)
Other comprehensive income before reclassification	15,940
Amounts reclassified from accumulated other comprehensive loss	(8,219)
Other comprehensive income	7,721
Balance at period end	(21,627)
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	(30,161)
Other comprehensive income before reclassification	13,974
Amounts reclassified from accumulated other comprehensive loss	(6,569)
Other comprehensive income	7,405
Balance at period end	(22,756)
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	813
Other comprehensive income before reclassification	1,966
Amounts reclassified from accumulated other comprehensive loss	(1,650)
Other comprehensive income	316
Balance at period end	$ 1,129