Net Income Per Common Share and Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic:
Net income available to common stockholders/unitholders	$ 80,975	$ 79,723	$ 272,333	$ 329,446
Weighted average number of shares/common units outstanding during the period (in shares)	66,052,108	65,994,896	66,047,990	65,759,450
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.23	$ 1.21	$ 4.12	$ 5.01
Diluted:
Net income available to common stockholders/unitholders	$ 80,975	$ 79,723	$ 272,333	$ 329,446
Net income available to common stockholders/unitholders, weighted average common shares (in shares)	66,103,812	66,078,283	66,093,004	65,836,965
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.22	$ 1.21	$ 4.12	$ 5.00
Essex Portfolio, L.P. [Member]
Basic:
Net income available to common stockholders/unitholders	$ 83,764	$ 82,444	$ 281,714	$ 340,735
Weighted average number of shares/common units outstanding during the period (in shares)	68,325,091	68,246,008	68,321,153	68,011,123
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.23	$ 1.21	$ 4.12	$ 5.01
Diluted:
Net income available to common stockholders/unitholders	$ 83,764	$ 82,444	$ 281,714	$ 340,735
Net income available to common stockholders/unitholders, weighted average common shares (in shares)	68,376,795	68,329,395	68,366,167	68,088,638
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.23	$ 1.21	$ 4.12	$ 5.00
Employee Stock Option [Member]
Basic:
Income effect of Dilutive Securities	$ 0	$ 0	$ 0	$ 0
Effect of dilutive securities (in shares)	51,704	83,387	45,014	77,515
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	150,852	0	160,252	2,352
Employee Stock Option [Member] | Essex Portfolio, L.P. [Member]
Basic:
Income effect of Dilutive Securities	$ 0	$ 0	$ 0	$ 0
Effect of dilutive securities (in shares)	51,704	83,387	45,014	77,515
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	150,852	0	160,252	2,352
Convertible Limited Partnership Units [Member]
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,272,983	2,251,112	2,273,163	2,251,673
Antidilutive securities excluded from computation of earnings per share, value	$ 2,800	$ 2,700	$ 9,400	$ 11,300