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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Basic:
Net income available to common stockholders/unitholders	$ 73,661	$ 99,335	$ 473,125	$ 310,468
Weighted average common shares/units (in shares)	65,232,837	65,850,524	65,561,820	65,757,914
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.13	$ 1.51	$ 7.22	$ 4.72
Effect of Dilutive Securities:
Stock options (in shares)	8,591	122,561	20,026	99,746
DownREIT units (in shares)			94,247	0
Diluted:
Net income available to common stockholders/unitholders	$ 73,661	$ 99,335	$ 473,712	$ 310,468
Weighted average common shares/units (in shares)	65,241,428	65,973,085	65,676,093	65,857,660
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.13	$ 1.51	$ 7.21	$ 4.71
Essex Portfolio, L.P.
Basic:
Net income available to common stockholders/unitholders	$ 76,254	$ 102,799	$ 489,668	$ 321,331
Weighted average common shares/units (in shares)	67,528,346	68,148,913	67,858,961	68,058,802
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.13	$ 1.51	$ 7.22	$ 4.72
Effect of Dilutive Securities:
Stock options (in shares)	8,591	122,561	20,026	99,746
DownREIT units (in shares)			94,247	0
Diluted:
Net income available to common stockholders/unitholders	$ 76,254	$ 102,799	$ 490,255	$ 321,331
Weighted average common shares/units (in shares)	67,536,937	68,271,474	67,973,234	68,158,548
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.13	$ 1.51	$ 7.21	$ 4.71
Convertible units
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,295,510	2,298,389	2,297,141	2,300,888
Income allocated to convertible OP Units	$ 2,600	$ 3,500	$ 16,500	$ 10,900
Stock options
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	493,567	0	299,046	0
Stock options | Essex Portfolio, L.P.
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	493,567	0
Subsidiaries | DownREIT Units
Effect of Dilutive Securities:
Income effect of Dilutive Securities			$ 587	$ 0
Subsidiaries | DownREIT Units | Essex Portfolio, L.P.
Effect of Dilutive Securities:
Income effect of Dilutive Securities			$ 587	$ 0