Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 125,002	$ 78,842	$ 371,566	$ 497,683
Adjustments to reconcile net income to net cash provided by operating activities:
Straight-lined rents			8,734	(15,485)
Depreciation and amortization			387,887	395,370
Amortization of discount on marketable securities			0	(6,598)
Amortization of discount and debt financing costs, net			7,987	5,177
Gain on sale of marketable securities			(2,499)	(124)
Income from early redemption of notes receivable			(4,747)	0
Provision for credit losses			(110)	100
Unrealized gains on equity securities recognized through income			(23,772)	(2,215)
Earnings from co-investments			(60,692)	(53,514)
Operating distributions from co-investments			78,360	41,202
Accrued interest from notes and other receivables			(12,253)	(1,574)
Gain on the sale of real estate and land			(142,993)	(39,251)
Equity-based compensation			5,399	4,923
Loss on early retirement of debt, net	0	19,114	18,982	23,820
Gain on remeasurement of co-investment	0	0	(2,260)	(234,694)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets			2,470	(5,088)
Accounts payable, accrued liabilities, and operating lease liabilities			62,699	43,095
Other liabilities			5,119	610
Net cash provided by operating activities			699,877	653,437
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired			(105,469)	(459,355)
Redevelopment			(39,092)	(41,592)
Development acquisitions of and additions to real estate under development			(45,381)	(90,273)
Capital expenditures on rental properties			(81,063)	(64,269)
Investments in notes receivable			(102,012)	(20,431)
Collections of notes and other receivables			88,744	98,711
Proceeds from insurance for property losses			591	612
Proceeds from dispositions of real estate			297,454	280,246
Contributions to co-investments			(223,175)	(61,056)
Changes in refundable deposits			(8,356)	96
Purchases of marketable securities			(23,740)	(38,909)
Sales and maturities of marketable securities			14,995	56,890
Non-operating distributions from co-investments			131,297	37,342
Net cash used in investing activities			(95,207)	(301,988)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes			745,505	1,452,808
Payments on unsecured debt and mortgage notes			(952,608)	(587,057)
Proceeds from lines of credit			601,435	1,038,426
Repayments of lines of credit			(558,773)	(1,093,426)
Retirement of common stock			(9,172)	(222,990)
Additions to deferred charges			(8,237)	(13,761)
Payments related to debt prepayment penalties			(18,342)	(19,605)
Net proceeds from issuance of common stock			(202)	(228)
Net proceeds from stock options exercised			17,847	14,865
Payments related to tax withholding for share-based compensation			(5,445)	(5,664)
Contributions from noncontrolling interest			1,900	0
Distributions to noncontrolling interest			(21,979)	(23,302)
Redemption of noncontrolling interest			(8,407)	(2,971)
Redemption of redeemable noncontrolling interest			(4,463)	0
Common stock dividends paid			(406,818)	(400,563)
Net cash (used in) provided by financing activities			(627,759)	136,532
Net (decrease) increase in unrestricted and restricted cash and cash equivalents			(23,089)	487,981
Unrestricted and restricted cash and cash equivalents at beginning of period			84,041	81,094	$ 81,094
Unrestricted and restricted cash and cash equivalents at end of period	60,952	569,075	60,952	569,075	84,041
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $5.0 million and $12.3 million capitalized in 2021 and 2020, respectively)			147,371	160,927
Operating cash flows from operating leases			5,225	5,192
Supplemental disclosure of noncash investing and financing activities:
Transfers between real estate under development and rental properties, net			222,055	252,946
Transfer from real estate under development to co-investments			1,853	1,387
Reclassifications to (from) redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest			4,922	(6,691)
Essex Portfolio, L.P.
Cash flows from operating activities:
Net income	125,002	78,842	371,566	497,683
Adjustments to reconcile net income to net cash provided by operating activities:
Straight-lined rents			8,734	(15,485)
Depreciation and amortization			387,887	395,370
Amortization of discount on marketable securities			0	(6,598)
Amortization of discount and debt financing costs, net			7,987	5,177
Gain on sale of marketable securities			(2,499)	(124)
Income from early redemption of notes receivable			(4,747)	0
Provision for credit losses			(110)	100
Unrealized gains on equity securities recognized through income			(23,772)	(2,215)
Earnings from co-investments			(60,692)	(53,514)
Operating distributions from co-investments			78,360	41,202
Accrued interest from notes and other receivables			(12,253)	(1,574)
Gain on the sale of real estate and land			(142,993)	(39,251)
Equity-based compensation			5,399	4,923
Loss on early retirement of debt, net	0	19,114	18,982	23,820
Gain on remeasurement of co-investment	0	0	(2,260)	(234,694)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets			2,470	(5,088)
Accounts payable, accrued liabilities, and operating lease liabilities			62,699	43,095
Other liabilities			5,119	610
Net cash provided by operating activities			699,877	653,437
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired			(105,469)	(459,355)
Redevelopment			(39,092)	(41,592)
Development acquisitions of and additions to real estate under development			(45,381)	(90,273)
Capital expenditures on rental properties			(81,063)	(64,269)
Investments in notes receivable			(102,012)	(20,431)
Collections of notes and other receivables			88,744	98,711
Proceeds from insurance for property losses			591	612
Proceeds from dispositions of real estate			297,454	280,246
Contributions to co-investments			(223,175)	(61,056)
Changes in refundable deposits			(8,356)	96
Purchases of marketable securities			(23,740)	(38,909)
Sales and maturities of marketable securities			14,995	56,890
Non-operating distributions from co-investments			131,297	37,342
Net cash used in investing activities			(95,207)	(301,988)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes			745,505	1,452,808
Payments on unsecured debt and mortgage notes			(952,608)	(587,057)
Proceeds from lines of credit			601,435	1,038,426
Repayments of lines of credit			(558,773)	(1,093,426)
Retirement of common stock			(9,172)	(222,990)
Additions to deferred charges			(8,237)	(13,761)
Payments related to debt prepayment penalties			(18,342)	(19,605)
Net proceeds from issuance of common stock			(202)	(228)
Net proceeds from stock options exercised			17,847	14,865
Payments related to tax withholding for share-based compensation			(5,445)	(5,664)
Contributions from noncontrolling interest			1,900	0
Distributions to noncontrolling interest			(6,323)	(6,287)
Redemption of noncontrolling interest			(8,407)	(2,971)
Redemption of redeemable noncontrolling interest			(4,463)	0
Common stock dividends paid			(422,474)	(417,578)
Net cash (used in) provided by financing activities			(627,759)	136,532
Net (decrease) increase in unrestricted and restricted cash and cash equivalents			(23,089)	487,981
Unrestricted and restricted cash and cash equivalents at beginning of period			84,041	81,094	81,094
Unrestricted and restricted cash and cash equivalents at end of period	$ 60,952	$ 569,075	60,952	569,075	$ 84,041
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $5.0 million and $12.3 million capitalized in 2021 and 2020, respectively)			147,371	160,927
Operating cash flows from operating leases			5,225	5,192
Supplemental disclosure of noncash investing and financing activities:
Transfers between real estate under development and rental properties, net			222,055	252,946
Transfer from real estate under development to co-investments			1,853	1,387
Reclassifications to (from) redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest			$ 4,922	$ (6,691)