Net Income Per Common Share and Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic:
Net income available to common stockholders	$ 100,440	$ 70,759	$ 191,358	$ 249,723
Weighted average number of shares/common units outstanding during the period (in shares)	66,047,751	65,729,074	66,045,897	65,639,775
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.52	$ 1.08	$ 2.90	$ 3.80
Diluted:
Income from continuing operations available to common stockholders	$ 100,440	$ 70,759	$ 191,358	$ 250,461
Adjusted income from continuing operations available to common stockholders (in shares)	66,096,349	65,819,694	66,088,803	65,942,018
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.52	$ 1.08	$ 2.90	$ 3.80
Essex Portfolio, L.P. [Member]
Basic:
Net income available to common stockholders	$ 103,900	$ 73,181	$ 197,950	$ 258,291
Weighted average number of shares/common units outstanding during the period (in shares)	68,320,849	67,980,761	68,319,151	67,891,734
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.52	$ 1.08	$ 2.90	$ 3.80
Diluted:
Income from continuing operations available to common stockholders	$ 103,900	$ 73,181	$ 197,950	$ 259,029
Adjusted income from continuing operations available to common stockholders (in shares)	68,369,447	68,071,381	68,362,057	68,193,977
Net income available to common stockholders/unitholders (in dollars per share)	$ 1.52	$ 1.08	$ 2.90	$ 3.80
Employee Stock Option [Member]
Basic:
Income effect of Dilutive Securities	$ 0	$ 0	$ 0	$ 0
Effect of dilutive securities (in shares)	48,598	90,620	42,906	91,515
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	185,181	8,240	185,470	23,619
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)	48,598	90,620	42,906	91,515
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	185,181	8,240	185,470	23,619
DownREIT Units [Member]
Basic:
Income effect of Dilutive Securities			$ 0	$ 738
Effect of dilutive securities (in shares)			0	210,728
DownREIT Units [Member] | Essex Portfolio, L.P. [Member]
Basic:
Income effect of Dilutive Securities			$ 0	$ 738
Effect of dilutive securities (in shares)			0	210,728
Convertible Limited Partnership Units [Member]
Diluted:
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,273,098	2,251,687	2,273,255	2,251,959
Antidilutive securities excluded from computation of earnings per share, value	$ 3,500	$ 2,500	$ 6,600	$ 8,600