Net Income Per Common Share and Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic:
Income from continuing operations available to common stockholders									$ 226,865	$ 116,859	$ 121,324
Income from continuing operations available to common stockholders (in shares)									64,871,717	56,546,959	37,248,960
Income from continuing operations available to common stockholders (in dollars per share)									$ 3.50	$ 2.07	$ 3.26
Income from discontinued operations available to common stockholders									$ 0	$ 0	$ 29,487
Income from discontinued operations available to common stockholders (in shares)									64,871,717	56,546,959	37,248,960
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.00	$ 0.79
Net income available to common stockholders	$ 79,624	$ 42,323	$ 45,555	$ 59,363	$ 40,175	$ 53,565	$ 1,207	$ 21,912	$ 226,865	$ 116,859	$ 150,811
Income available to common stockholders (in dollars per share)	$ 1.22	$ 0.65	$ 0.70	$ 0.92	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 3.50	$ 2.07	$ 4.05
Effect of Dilutive Securities									$ 0	$ 0	$ 0
Effect of Dilutive Securities (in shares)									189,968	149,566	86,335
Diluted:
Income from continuing operations available to common stockholders									$ 226,865	$ 116,859	$ 121,324
Income from continuing operations available to common stockholders (in shares)									65,061,685	56,696,525	37,335,295
Income from continuing operations available to common stockholders (in dollars per share)									$ 3.49	$ 2.06	$ 3.25
Income from discontinued operations available to common stockholders									$ 0	$ 0	$ 29,487
Income from discontinued operations available to common stockholders (in shares)									65,061,685	56,696,525	37,335,295
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.00	$ 0.79
Total income (Diluted)									$ 226,865	$ 116,859	$ 150,811
Total income per common share amount (in dollars per share)	$ 1.22	$ 0.65	$ 0.70	$ 0.92	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 3.49	$ 2.06	$ 4.04
Convertible Limited Partnership Units [Member]
Diluted:
Anti-dilutive securities (in shares)									2,182,467	2,224,707	2,131,425
DownREIT Units [Member]
Diluted:
Anti-dilutive securities (in shares)									963,172
Stock Options [Member]
Diluted:
Anti-dilutive securities (in shares)									54,100	10,843	168,325
Essex Portfolio, L.P. [Member]
Basic:
Income from continuing operations available to common stockholders									$ 234,689	$ 121,726	$ 128,576
Income from continuing operations available to common stockholders (in shares)									67,054,184	58,771,666	39,380,385
Income from continuing operations available to common stockholders (in dollars per share)									$ 3.50	$ 2.07	$ 3.27
Income from discontinued operations available to common stockholders									$ 0	$ 0	$ 31,173
Income from discontinued operations available to common stockholders (in shares)									67,054,184	58,771,666	39,380,385
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.00	$ 0.79
Net income available to common stockholders	$ 82,333	$ 43,794	$ 47,088	$ 61,474	$ 41,599	$ 55,382	$ 1,416	$ 23,329	$ 234,689	$ 121,726	$ 159,749
Income available to common stockholders (in dollars per share)	$ 1.22	$ 0.65	$ 0.70	$ 0.93	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 3.50	$ 2.07	$ 4.06
Effect of Dilutive Securities									$ 0	$ 0	$ 0
Effect of Dilutive Securities (in shares)									189,968	149,566	86,335
Diluted:
Income from continuing operations available to common stockholders									$ 234,689	$ 121,726	$ 128,576
Income from continuing operations available to common stockholders (in shares)									67,244,152	58,921,232	39,466,720
Income from continuing operations available to common stockholders (in dollars per share)									$ 3.49	$ 2.07	$ 3.26
Income from discontinued operations available to common stockholders									$ 0	$ 0	$ 31,173
Income from discontinued operations available to common stockholders (in shares)									67,244,152	58,921,232	39,466,720
Income from discontinued operations available to common stockholders (in dollars per share)									$ 0.00	$ 0.00	$ 0.79
Total income (Diluted)									$ 234,689	$ 121,726	$ 159,749
Total income per common share amount (in dollars per share)	$ 1.22	$ 0.65	$ 0.70	$ 0.92	$ 0.63	$ 0.85	$ 0.02	$ 0.58	$ 3.49	$ 2.07	$ 4.05