Net Income Per Common Share and Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic:
Net income available to common stockholders	$ 90,918	$ 178,964
Weighted average number of shares/common units outstanding during the period (in shares)	66,044,022	65,549,484
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.38	$ 2.73
Diluted:
Income from continuing operations available to common stockholders	$ 90,918	$ 179,337
Adjusted income from continuing operations available to common stockholders (in shares)	66,082,517	65,859,490
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.38	$ 2.72
Essex Portfolio, L.P. [Member]
Basic:
Net income available to common stockholders	$ 94,050	$ 185,110
Weighted average number of shares/common units outstanding during the period (in shares)	68,317,435	67,801,718
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.38	$ 2.73
Diluted:
Income from continuing operations available to common stockholders	$ 94,050	$ 185,483
Adjusted income from continuing operations available to common stockholders (in shares)	68,355,930	68,111,724
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.38	$ 2.72
Employee Stock Option [Member]
Basic:
Income effect of Dilutive Securities	$ 0	$ 0
Effect of dilutive securities (in shares)	38,495	96,778
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	364,068	225,895
Employee Stock Option [Member] | Essex Portfolio, L.P. [Member]
Basic:
Income effect of Dilutive Securities	$ 0	$ 0
Effect of dilutive securities (in shares)	38,495	96,778
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	364,068	225,895
Convertible Limited Partnership Units [Member]
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,273,413	2,252,234
Antidilutive securities excluded from computation of earnings per share, value	$ 3,100	$ 6,100
DownREIT Units [Member]
Basic:
Income effect of Dilutive Securities	$ 0	$ 373
Effect of dilutive securities (in shares)	0	213,228
DownREIT Units [Member] | Essex Portfolio, L.P. [Member]
Basic:
Income effect of Dilutive Securities	$ 0	$ 373
Effect of dilutive securities (in shares)	0	213,228