Organization and Basis of Presentation - Accumulated Other Comprehensive Income Summary (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	$ 6,022,672
Balance at period end	6,221,041
AOCI Attributable to Parent [Member] | Essex Portfolio, L.P. [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(49,356)
Other comprehensive income before reclassification	(5,095)
Amounts reclassified from accumulated other comprehensive loss	6,227
Other comprehensive income	1,132
Balance at period end	(48,224)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(51,452)
Other comprehensive income before reclassification	(4,929)
Amounts reclassified from accumulated other comprehensive loss	6,024
Other comprehensive income	1,095
Balance at period end	(50,357)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(56,003)
Other comprehensive income before reclassification	(4,403)
Amounts reclassified from accumulated other comprehensive loss	6,024
Other comprehensive income	1,621
Balance at period end	(54,382)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	4,551
Other comprehensive income before reclassification	(526)
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income	(526)
Balance at period end	$ 4,025