Organization and Basis of Presentation - Accumulated Other Comprehensive Loss - Partnership (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	$ 6,292,237
Balance at period end	6,438,027
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	9,612
Amounts reclassified from accumulated other comprehensive loss	(5,726)
Other comprehensive income (loss)	3,886
Balance at period end	(25,462)
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	8,925
Amounts reclassified from accumulated other comprehensive loss	(4,108)
Other comprehensive income (loss)	4,817
Balance at period end	(25,344)
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	687
Amounts reclassified from accumulated other comprehensive loss	(1,618)
Other comprehensive income (loss)	(931)
Balance at period end	$ (118)