Consolidated Statements of Capital - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 109,662	$ 187,551	$ 204,517	$ 86,907	$ 458,043	$ 438,410	$ 248,239
Reversal of unrealized gains upon the sale of marketable securities					(1,909)	(4,848)	0
Change in fair value of derivatives and amortization of swap settlements					12,744	15,926	7,893
Changes in fair value of marketable securities, net					3,284	(828)	1,865
Issuance of common stock under:
Sale of common stock by the general partner, net					$ 89,055	$ (384)	332,137
Sale of common stock by the general partner, net (in shares)					345,444	0
Retirement of common stock, net						$ (1,045)
Changes in the redemption value of redeemable noncontrolling interest					$ (65)	768	(2,615)
Reclassification of noncontrolling interest to redeemable noncontrolling interest							(19,772)
Contributions from noncontrolling interest					22,506
Distributions to noncontrolling interests					(27,051)	(25,854)	(21,705)
Redemptions					(28,580)	(2,511)	(2,621)
Essex Portfolio, L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Balances		6,292,237		6,337,023	6,292,237	6,337,023	6,136,068
Net income	109,662	187,551	204,517	86,907	458,043	438,410	248,239
Reversal of unrealized gains upon the sale of marketable securities					(1,909)	(4,848)	0
Change in fair value of derivatives and amortization of swap settlements					12,744	15,926	7,893
Changes in fair value of marketable securities, net					3,284	(828)	1,865
Issuance of common stock under:
General partner's stock based compensation, net					26,635	18,949	26,540
Sale of common stock by the general partner, net					89,055	(384)	332,137
Equity based compensation costs					11,302	10,899	9,646
Redemption of Series H preferred units						(73,750)
Retirement of common stock, net						(1,045)
Changes in the redemption value of redeemable noncontrolling interest					(65)	768	(2,615)
Reclassification of noncontrolling interest to redeemable noncontrolling interest							(19,772)
Contributions from noncontrolling interest					22,506
Distributions to noncontrolling interests					(11,078)	(11,296)	(8,751)
Redemptions					(28,580)	(2,511)	(2,621)
Distributions declared					(477,349)	(435,076)	(391,606)
Balances	6,396,825		6,292,237		6,396,825	6,292,237	6,337,023
Essex Portfolio, L.P. [Member] | Accumulated other comprehensive loss, net [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Balances		(29,348)		(39,598)	(29,348)	(39,598)	(49,356)
Reversal of unrealized gains upon the sale of marketable securities					(1,909)	(4,848)
Change in fair value of derivatives and amortization of swap settlements					12,744	15,926	7,893
Changes in fair value of marketable securities, net					3,284	(828)	1,865
Issuance of common stock under:
Balances	(15,229)		(29,348)		(15,229)	(29,348)	(39,598)
Essex Portfolio, L.P. [Member] | Noncontrolling Interest [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Balances		47,873		49,642	47,873	49,642	62,635
Net income					10,159	9,342	8,295
Issuance of common stock under:
Changes in the redemption value of redeemable noncontrolling interest					(65)	596
Reclassification of noncontrolling interest to redeemable noncontrolling interest							(12,115)
Contributions from noncontrolling interest					22,506
Distributions to noncontrolling interests					(11,078)	(11,296)	(8,751)
Redemptions					(2,985)	(411)	(422)
Balances	66,410		47,873		66,410	47,873	49,642
Essex Portfolio, L.P. [Member] | General Partner [Member] | Common Equity [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Balances		$ 6,224,276		$ 6,208,535	$ 6,224,276	$ 6,208,535	$ 6,002,915
Balances (in shares)		65,528,000		65,379,000	65,528,000	65,379,000	63,683,000
Net income					$ 433,059	$ 411,124	$ 226,865
Issuance of common stock under:
General partner's stock based compensation, net					$ 26,635	$ 18,949	$ 26,540
General partner's stock based compensation, net (in shares)					179,000	140,000	207,000
Sale of common stock by the general partner, net					$ 89,055	$ (384)	$ 332,137
Sale of common stock by the general partner, net (in shares)					345,000		1,482,000
Equity based compensation costs					$ 9,529	8,246	$ 5,946
Retirement of common stock, net						$ (1,045)
Retirement of common stock, net (in shares)						(5,000)
Changes in the redemption value of redeemable noncontrolling interest					(136)	$ 172	(2,615)
Reclassification of noncontrolling interest to redeemable noncontrolling interest							(7,657)
Redemptions					$ (25,190)	$ (2,117)	$ (2,199)
Redemptions (in shares)					(2,000)	(14,000)	(7,000)
Distributions declared					$ (461,376)	$ (419,204)	$ (373,397)
Balances	$ 6,295,852		$ 6,224,276		$ 6,295,852	$ 6,224,276	$ 6,208,535
Balances (in shares)	66,054,000		65,528,000		66,054,000	65,528,000	65,379,000
Essex Portfolio, L.P. [Member] | General Partner [Member] | Preferred Equity [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Balances		$ 0		$ 71,209	$ 0	$ 71,209	$ 71,209
Net income						3,855	5,255
Issuance of common stock under:
Redemption of Series H preferred units						(73,750)
Distributions declared						(1,314)	(5,255)
Balances	$ 0		$ 0		0	0	71,209
Essex Portfolio, L.P. [Member] | Limited Partner [Member] | Common Equity [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Balances		$ 49,436		$ 47,235	$ 49,436	$ 47,235	$ 48,665
Balances (in shares)		2,237,000		2,215,000	2,237,000	2,215,000	2,168,000
Net income					$ 14,825	$ 14,089	$ 7,824
Issuance of common stock under:
Equity based compensation costs					$ 1,773	$ 2,653	$ 3,700
Equity-based compensation costs (in shares)					33,000	37,000	54,000
Changes in the redemption value of redeemable noncontrolling interest					$ 136
Reclassification of noncontrolling interest to redeemable noncontrolling interest							$ 0
Redemptions					$ (405)	$ 17	$ 0
Redemptions (in shares)					(2,000)	(15,000)	(7,000)
Distributions declared					$ (15,973)	$ (14,558)	$ (12,954)
Balances	$ 49,792		$ 49,436		$ 49,792	$ 49,436	$ 47,235
Balances (in shares)	2,268,000		2,237,000		2,268,000	2,237,000	2,215,000