Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 78,842	$ 105,700	$ 497,683	$ 329,266
Adjustments to reconcile net income to net cash provided by operating activities:
Straight-lined rents			(15,485)	(230)
Depreciation and amortization			395,370	360,842
Amortization of discount on marketable securities			(6,598)	(16,673)
Amortization of discount and debt financing costs, net			5,177	3,454
Gain on sale of marketable securities			(124)	(737)
Provision for credit losses			100
Unrealized gains on equity securities recognized through income			(2,215)	(4,280)
Company's share of gain on the sales of co-investments			0	(870)
Earnings from co-investments			(53,514)	(54,065)
Operating distributions from co-investments			41,202	64,628
Accrued interest from notes and other receivables			(1,574)	(4,523)
Gain on the sale of real estate and land			(39,251)	0
Equity-based compensation			4,923	6,748
Loss (gain) on early retirement of debt, net	19,114	(5,475)	23,820	(7,143)
Gain on remeasurement of co-investment	0	0	(234,694)	(31,535)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets			(5,088)	(3,962)
Accounts payable, accrued liabilities, and operating lease liabilities			43,095	64,281
Other liabilities			610	1,726
Net cash provided by operating activities			653,437	706,927
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired			(459,355)	(93,389)
Redevelopment			(41,592)	(55,027)
Development acquisitions of and additions to real estate under development			(90,273)	(130,593)
Capital expenditures on rental properties			(64,269)	(69,348)
Investments in notes receivable			(20,431)	(140,663)
Collections of notes and other receivables			98,711	2,500
Proceeds from insurance for property losses			612	3,599
Proceeds from dispositions of real estate			280,246	0
Contributions to co-investments			(61,056)	(306,233)
Changes in refundable deposits			96	325
Purchases of marketable securities			(38,909)	(42,653)
Sales and maturities of marketable securities			56,890	57,165
Non-operating distributions from co-investments			37,342	70,064
Net cash used in investing activities			(301,988)	(704,253)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes			1,452,808	892,762
Payments on unsecured debt and mortgage notes			(587,057)	(800,746)
Proceeds from lines of credit			1,038,426	1,485,034
Repayments of lines of credit			(1,093,426)	(1,265,034)
Retirement of common stock			(222,990)	(56,989)
Additions to deferred charges			(13,761)	(9,446)
Payments related to debt prepayments penalties			(19,605)	0
Net proceeds from issuance of common stock			(228)	72,549
Net proceeds from stock options exercised			14,865	36,422
Payments related to tax withholding for share-based compensation			(5,664)	(3,515)
Distributions to noncontrolling interest			(23,302)	(20,269)
Redemption of noncontrolling interest			(2,971)	(14,180)
Redemption of redeemable noncontrolling interest			0	(73)
Common stock dividends paid			(400,563)	(378,858)
Net cash provided by (used in) financing activities			136,532	(62,343)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents			487,981	(59,669)
Unrestricted and restricted cash and cash equivalents at beginning of period			81,094	151,395	$ 151,395
Unrestricted and restricted cash and cash equivalents at end of period	569,075	91,726	569,075	91,726	81,094
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $12.3 million and $19.0 million capitalized in 2020 and 2019, respectively)			160,927	145,001
Operating cash flows from operating leases			5,192	5,097
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT units in connection with acquisition of real estate			0	65,472
Transfers between real estate under development and rental properties, net			252,946	14,501
Transfer from real estate under development to co-investments			1,387	106
Reclassifications (from) to redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest			(6,691)	3,675
Initial recognition of operating lease right-of-use assets			0	77,645
Initial recognition of operating lease liabilities			0	79,693
Debt assumed in connection with acquisition			0	143,006
Interest capitalized			12,300	19,000
Essex Portfolio, L.P.
Cash flows from operating activities:
Net income	78,842	105,700	497,683	329,266
Adjustments to reconcile net income to net cash provided by operating activities:
Straight-lined rents			(15,485)	(230)
Depreciation and amortization			395,370	360,842
Amortization of discount on marketable securities			(6,598)	(16,673)
Amortization of discount and debt financing costs, net			5,177	3,454
Gain on sale of marketable securities			(124)	(737)
Provision for credit losses			100	0
Unrealized gains on equity securities recognized through income			(2,215)	(4,280)
Company's share of gain on the sales of co-investments			0	(870)
Earnings from co-investments			(53,514)	(54,065)
Operating distributions from co-investments			41,202	64,628
Accrued interest from notes and other receivables			(1,574)	(4,523)
Gain on the sale of real estate and land			(39,251)	0
Equity-based compensation			4,923	6,748
Loss (gain) on early retirement of debt, net	19,114	(5,475)	23,820	(7,143)
Gain on remeasurement of co-investment	0	0	(234,694)	(31,535)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets			(5,088)	(3,962)
Accounts payable, accrued liabilities, and operating lease liabilities			43,095	64,281
Other liabilities			610	1,726
Net cash provided by operating activities			653,437	706,927
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired			(459,355)	(93,389)
Redevelopment			(41,592)	(55,027)
Development acquisitions of and additions to real estate under development			(90,273)	(130,593)
Capital expenditures on rental properties			(64,269)	(69,348)
Investments in notes receivable			(20,431)	(140,663)
Collections of notes and other receivables			98,711	2,500
Proceeds from insurance for property losses			612	3,599
Proceeds from dispositions of real estate			280,246	0
Contributions to co-investments			(61,056)	(306,233)
Changes in refundable deposits			96	325
Purchases of marketable securities			(38,909)	(42,653)
Sales and maturities of marketable securities			56,890	57,165
Non-operating distributions from co-investments			37,342	70,064
Net cash used in investing activities			(301,988)	(704,253)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes			1,452,808	892,762
Payments on unsecured debt and mortgage notes			(587,057)	(800,746)
Proceeds from lines of credit			1,038,426	1,485,034
Repayments of lines of credit			(1,093,426)	(1,265,034)
Retirement of common stock			(222,990)	(56,989)
Additions to deferred charges			(13,761)	(9,446)
Payments related to debt prepayments penalties			(19,605)	0
Net proceeds from issuance of common stock			(228)	72,549
Net proceeds from stock options exercised			14,865	36,422
Payments related to tax withholding for share-based compensation			(5,664)	(3,515)
Distributions to noncontrolling interest			(6,287)	(5,978)
Redemption of noncontrolling interest			(2,971)	(14,180)
Redemption of redeemable noncontrolling interest			0	(73)
Common stock dividends paid			(417,578)	(393,149)
Net cash provided by (used in) financing activities			136,532	(62,343)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents			487,981	(59,669)
Unrestricted and restricted cash and cash equivalents at beginning of period			81,094	151,395	151,395
Unrestricted and restricted cash and cash equivalents at end of period	$ 569,075	$ 91,726	569,075	91,726	$ 81,094
Supplemental disclosure of cash flow information:
Cash paid for interest (net of $12.3 million and $19.0 million capitalized in 2020 and 2019, respectively)			160,927	145,001
Operating cash flows from operating leases			5,192	5,097
Supplemental disclosure of noncash investing and financing activities:
Issuance of DownREIT units in connection with acquisition of real estate			0	65,472
Transfers between real estate under development and rental properties, net			252,946	14,501
Transfer from real estate under development to co-investments			1,387	106
Reclassifications (from) to redeemable noncontrolling interest to/from additional paid in capital and noncontrolling interest			(6,691)	3,675
Initial recognition of operating lease right-of-use assets			0	77,645
Initial recognition of operating lease liabilities			0	79,693
Debt assumed in connection with acquisition			0	143,006
Interest capitalized			$ 12,300	$ 19,000