Net Income Per Common Share and Net Income Per Common Unit (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic:
Income from continuing operations available to common stockholders									$ 116,859	$ 121,324	$ 108,532
Income from continuing operations available to common stockholders (in shares)									56,546,959	37,248,960	35,032,491
Income from continuing operations available to common stockholders (in dollars per share)									$ 2.07	$ 3.26	$ 3.10
Income from discontinued operations available to common stockholders									0	29,487	11,280
Income from discontinued operations available to common stockholders (in shares)									56,546,959	37,248,960	35,032,491
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.79	$ 0.32
Net income available to common stockholders	40,175	53,565	1,207	21,912	31,874	68,788	24,946	25,203	116,859	150,811	119,812
Income available to common stockholders (in dollars per share)	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 0.85	$ 1.84	$ 0.67	$ 0.68	$ 2.07	$ 4.05	$ 3.42
Effect of Dilutive Securities									0	0	0
Effect of Dilutive Securities (in shares)									149,566	86,335	92,430
Diluted:
Income from continuing operations available to common stockholders									116,859	121,324	108,532
Income from continuing operations available to common stockholders (in shares)									56,696,525	37,335,295	35,124,921
Income from continuing operations available to common stockholders (in dollars per share)									$ 2.06	$ 3.25	$ 3.09
Income from discontinued operations available to common stockholders									0	29,487	11,280
Income from discontinued operations available to common stockholders (in shares)									56,696,525	37,335,295	35,124,921
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.79	$ 0.32
Total income (Diluted)									116,859	150,811	119,812
Total income per common share amount (in dollars per share)	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 0.85	$ 1.84	$ 0.67	$ 0.68	$ 2.06	$ 4.04	$ 3.41
Convertible Limited Partnership Units [Member]
Diluted:
Anti-dilutive securities (in shares)									2,224,707	2,131,425	2,219,046
Stock Options [Member]
Diluted:
Anti-dilutive securities (in shares)									10,843	168,325	263,613
Essex Portfolio, L.P. [Member]
Basic:
Income from continuing operations available to common stockholders									121,726	128,576	115,834
Income from continuing operations available to common stockholders (in shares)									58,771,666	39,380,385	37,251,537
Income from continuing operations available to common stockholders (in dollars per share)									$ 2.07	$ 3.27	$ 3.11
Income from discontinued operations available to common stockholders									0	31,173	11,937
Income from discontinued operations available to common stockholders (in shares)									58,771,666	39,380,385	37,251,537
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.79	$ 0.32
Net income available to common stockholders	41,599	55,382	1,416	23,329	33,776	72,777	26,493	26,703	121,726	159,749	127,771
Income available to common stockholders (in dollars per share)	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 0.87	$ 1.84	$ 0.67	$ 0.68	$ 2.07	$ 4.06	$ 3.43
Effect of Dilutive Securities									0	0	0
Effect of Dilutive Securities (in shares)									149,566	86,335	92,430
Diluted:
Income from continuing operations available to common stockholders									121,726	128,576	115,834
Income from continuing operations available to common stockholders (in shares)									58,921,232	39,466,720	37,343,967
Income from continuing operations available to common stockholders (in dollars per share)									$ 2.07	$ 3.26	$ 3.10
Income from discontinued operations available to common stockholders									0	31,173	11,937
Income from discontinued operations available to common stockholders (in shares)									58,921,232	39,466,720	37,343,967
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.79	$ 0.32
Total income (Diluted)									$ 121,726	$ 159,749	$ 127,771
Total income per common share amount (in dollars per share)	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 0.86	$ 1.84	$ 0.67	$ 0.68	$ 2.07	$ 4.05	$ 3.42