Summary of Critical and Significant Accounting Policies Summary of Critical and Significant Accounting Policies - AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	$ 6,277,406
Other comprehensive income (loss) before reclassification	15,229
Amounts reclassified from accumulated other comprehensive loss	(7,766)
Other comprehensive income	5,229
Balance at December 31, 2018	6,267,073
Change in fair value and amortization of swap agreements [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(20,641)
Cumulative effect upon adoption of ASU No. 2016-01		$ 0
Other comprehensive income (loss) before reclassification	15,343
Amounts reclassified from accumulated other comprehensive loss	(7,779)
Other comprehensive income	7,564
Balance at December 31, 2018	(13,077)
Unrealized gains on available for sale securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	2,195
Cumulative effect upon adoption of ASU No. 2016-01		(2,234)
Other comprehensive income (loss) before reclassification	(114)
Amounts reclassified from accumulated other comprehensive loss	13
Other comprehensive income	(2,335)
Balance at December 31, 2018	(140)
Accumulated other comprehensive loss, net [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(18,446)
Cumulative effect upon adoption of ASU No. 2016-01		(2,234)
Balance at December 31, 2018	(13,217)
Essex Portfolio, L.P. [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassification	15,753
Amounts reclassified from accumulated other comprehensive loss	(8,034)
Other comprehensive income	5,491
Essex Portfolio, L.P. [Member] | Change in fair value and amortization of swap agreements [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(17,417)
Cumulative effect upon adoption of ASU No. 2016-01		0
Other comprehensive income (loss) before reclassification	15,871
Amounts reclassified from accumulated other comprehensive loss	(8,047)
Other comprehensive income	7,824
Balance at December 31, 2018	(9,593)
Essex Portfolio, L.P. [Member] | Unrealized gains on available for sale securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	2,188
Cumulative effect upon adoption of ASU No. 2016-01		(2,228)
Other comprehensive income (loss) before reclassification	(118)
Amounts reclassified from accumulated other comprehensive loss	13
Other comprehensive income	(2,333)
Balance at December 31, 2018	(145)
Essex Portfolio, L.P. [Member] | Accumulated other comprehensive loss, net [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(15,229)
Cumulative effect upon adoption of ASU No. 2016-01		$ (2,228)
Balance at December 31, 2018	$ (9,738)