Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 458,043	$ 438,410	$ 248,239
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	468,881	441,682	453,423
Amortization of discount on marketable securities and other investments	(15,119)	(14,211)	(12,389)
Amortization of (premium) discount and financing costs, net	(5,948)	(15,234)	(19,361)
Gain on sale of marketable securities and other investments	(1,909)	(5,719)	(598)
Company's share of gain on the sales of co-investments	(44,837)	(13,046)	0
Earnings from co-investments	(41,608)	(35,652)	(21,861)
Operating distributions from co-investments	76,764	60,472	46,608
Gain on the sale of real estate and land	(26,423)	(154,561)	(47,333)
Equity-based compensation	9,286	9,811	6,061
Loss on early retirement of debt, net	1,796	606	6,114
Gain on remeasurement of co-investment	(88,641)	0	(34,014)
Changes in operating assets and liabilities:
Prepaid expenses, receivables and other assets	(8,860)	(2,328)	267
Accounts payable and accrued liabilities	(15,104)	2,087	(8,875)
Other liabilities	(170)	(496)	1,887
Net cash provided by operating activities	766,151	711,821	618,168
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures	(206,194)	(315,632)	(515,726)
Redevelopment	(69,928)	(83,927)	(99,346)
Development acquisitions of and additions to real estate under development	(137,733)	(75,367)	(157,900)
Capital expenditures on rental properties	(70,986)	(60,013)	(57,277)
Acquisition of membership interest in co-investments	0	0	(115,724)
Collections of notes and other receivables	55,000	4,070	0
Investments in notes receivable	(106,461)	(24,070)	0
Proceeds from insurance for property losses	648	5,543	16,811
Proceeds from dispositions of real estate	132,039	239,289	319,008
Contributions to co-investments	(293,363)	(183,989)	(127,879)
Changes in restricted cash and refundable deposits	89,712	(14,138)	(14,068)
Purchases of marketable securities	(67,893)	(18,779)	(14,300)
Sales and maturities of marketable securities and other investments	35,481	30,458	8,907
Non-operating distributions from co-investments	162,439	76,231	31,938
Net cash used in investing activities	(477,239)	(420,324)	(725,556)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	597,981	669,282	641,816
Payments on unsecured debt and mortgage notes	(561,160)	(532,020)	(261,734)
Proceeds from lines of credit	982,246	596,106	704,039
Repayments of lines of credit	(928,246)	(486,106)	(935,617)
Repayment of cumulative redeemable preferred stock	0	(73,750)	0
Retirement of common stock	0	(1,045)	0
Additions to deferred charges	(4,108)	(7,926)	(8,034)
Net proceeds from issuance of common stock	89,055	(384)	332,137
Net proceeds from stock options exercised	26,635	18,949	26,540
Payments related to tax withholding for share-based compensation	(316)	(386)	(758)
Distributions to noncontrolling interest	(26,552)	(25,334)	(21,055)
Redemption of noncontrolling interest	(28,580)	(2,511)	(2,621)
Redemption of redeemable noncontrolling interest	(5,543)	0	0
Common and preferred stock/units dividends paid and preferred interest distributions paid	(450,625)	(411,134)	(367,257)
Net cash (used in) provided by financing activities	(309,213)	(256,259)	107,456
Cash acquired from consolidation of co-investment	0	0	4,005
Net increase in cash and cash equivalents	(20,301)	35,238	4,073
Cash and cash equivalents at beginning of year	64,921	29,683	25,610
Cash and cash equivalents at end of year	44,620	64,921	29,683
Supplemental disclosure of cash flow information:
Cash paid for interest, net of capitalized interest	212,163	203,743	181,106
Interest capitalized	13,860	12,486	15,571
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT limited partnership units in connection with acquisition of real estate	22,506	0	0
Transfers between real estate under development to rental properties, net	2,413	104,159	308,704
Transfer from real estate under development to co-investments	5,075	9,919	6,234
Reclassifications to (from) redeemable noncontrolling interest to or from additional paid in capital and noncontrolling interest	65	(768)	22,387
Debt assumed in connection with acquisition	51,882	48,832	114,435
Debt deconsolidated in connection with BEX II transaction	0	20,195	0
Essex Portfolio, L.P. [Member]
Cash flows from operating activities:
Net income	458,043	438,410	248,239
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	468,881	441,682	453,423
Amortization of discount on marketable securities and other investments	(15,119)	(14,211)	(12,389)
Amortization of (premium) discount and financing costs, net	(5,948)	(15,234)	(19,361)
Gain on sale of marketable securities and other investments	(1,909)	(5,719)	(598)
Company's share of gain on the sales of co-investments	(44,837)	(13,046)	0
Earnings from co-investments	(41,608)	(35,652)	(21,861)
Operating distributions from co-investments	76,764	60,472	46,608
Gain on the sale of real estate and land	(26,423)	(154,561)	(47,333)
Equity-based compensation	9,286	9,811	6,061
Loss on early retirement of debt, net	1,796	606	6,114
Gain on remeasurement of co-investment	(88,641)	0	(34,014)
Changes in operating assets and liabilities:
Prepaid expenses, receivables and other assets	(8,860)	(2,328)	267
Accounts payable and accrued liabilities	(15,104)	2,087	(8,875)
Other liabilities	(170)	(496)	1,887
Net cash provided by operating activities	766,151	711,821	618,168
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures	(206,194)	(315,632)	(515,726)
Redevelopment	(69,928)	(83,927)	(99,346)
Development acquisitions of and additions to real estate under development	(137,733)	(75,367)	(157,900)
Capital expenditures on rental properties	(70,986)	(60,013)	(57,277)
Acquisition of membership interest in co-investments	0	0	(115,724)
Collections of notes and other receivables	55,000	4,070	0
Investments in notes receivable	(106,461)	(24,070)	0
Proceeds from insurance for property losses	648	5,543	16,811
Proceeds from dispositions of real estate	132,039	239,289	319,008
Contributions to co-investments	(293,363)	(183,989)	(127,879)
Changes in restricted cash and refundable deposits	89,712	(14,138)	(14,068)
Purchases of marketable securities	(67,893)	(18,779)	(14,300)
Sales and maturities of marketable securities and other investments	35,481	30,458	8,907
Non-operating distributions from co-investments	162,439	76,231	31,938
Net cash used in investing activities	(477,239)	(420,324)	(725,556)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	597,981	669,282	641,816
Payments on unsecured debt and mortgage notes	(561,160)	(532,020)	(261,734)
Proceeds from lines of credit	982,246	596,106	704,039
Repayments of lines of credit	(928,246)	(486,106)	(935,617)
Repayment of cumulative redeemable preferred stock	0	(73,750)	0
Retirement of common stock	0	(1,045)	0
Additions to deferred charges	(4,108)	(7,926)	(8,034)
Net proceeds from issuance of common stock	89,055	(384)	332,137
Net proceeds from stock options exercised	26,635	18,949	26,540
Payments related to tax withholding for share-based compensation	(316)	(386)	(758)
Distributions to noncontrolling interest	(7,752)	(6,960)	(7,615)
Redemption of noncontrolling interest	(28,580)	(2,511)	(2,621)
Redemption of redeemable noncontrolling interest	(5,543)	0	0
Common and preferred stock/units dividends paid and preferred interest distributions paid	(469,425)	(429,508)	(380,697)
Net cash (used in) provided by financing activities	(309,213)	(256,259)	107,456
Cash acquired from consolidation of co-investment	0	0	4,005
Net increase in cash and cash equivalents	(20,301)	35,238	4,073
Cash and cash equivalents at beginning of year	64,921	29,683	25,610
Cash and cash equivalents at end of year	44,620	64,921	29,683
Supplemental disclosure of cash flow information:
Cash paid for interest, net of capitalized interest	212,163	203,743	181,106
Interest capitalized	13,860	12,486	15,571
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT limited partnership units in connection with acquisition of real estate	22,506	0	0
Transfers between real estate under development to rental properties, net	2,413	104,159	308,704
Transfer from real estate under development to co-investments	5,075	9,919	6,234
Reclassifications to (from) redeemable noncontrolling interest to or from additional paid in capital and noncontrolling interest	65	(768)	22,387
Debt assumed in connection with acquisition	51,882	48,832	114,435
Debt deconsolidated in connection with BEX II transaction	$ 0	$ 20,195	$ 0