Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 599,332	$ 464,448	$ 413,599
Adjustments to reconcile net income to net cash provided by operating activities:
Straight-lined rents	(19,426)	(1,218)	(347)
Depreciation and amortization	525,497	483,750	479,884
Amortization of discount on marketable securities	(19,075)	(28,491)	(17,637)
Amortization of (premium) discount and debt financing costs, net	6,674	5,689	(2,587)
Gain on sale of marketable securities	(2,131)	(1,271)	(737)
Provision for credit losses	687	0	0
Unrealized (gains) losses on equity securities recognized through income	(12,515)	(5,710)	5,159
Company's share of gain on the sales of co-investments	(2,225)	(51,097)	(10,569)
Earnings from co-investments	(64,287)	(61,039)	(78,563)
Operating distributions from co-investments	74,419	99,277	99,593
Accrued interest from notes and other receivables	(3,683)	(6,012)	(5,436)
Impairment loss	1,825	7,105	0
(Gain) loss on the sale of real estate and land	(64,967)	3,164	(61,861)
Equity-based compensation	8,157	7,010	7,135
Loss (gain) on early retirement of debt, net	22,883	(3,717)	0
Gain on remeasurement of co-investment	(234,694)	(31,535)	(1,253)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets	(3,730)	6,969	(856)
Accounts payable, accrued liabilities, and operating lease liabilities	(10,382)	29,551	(145)
Other liabilities	749	2,206	1,175
Net cash provided by operating activities	803,108	919,079	826,554
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired	(460,421)	(133,825)	(15,311)
Redevelopment	(48,980)	(70,295)	(73,000)
Development acquisitions of and additions to real estate under development	(108,781)	(158,234)	(182,772)
Capital expenditures on rental properties	(90,085)	(101,689)	(81,684)
Investments in notes receivable	(135,343)	(231,400)	0
Collections of notes and other receivables	98,711	168,720	29,500
Proceeds from insurance for property losses	723	3,734	1,408
Proceeds from dispositions of real estate	339,165	23,214	347,587
Contributions to co-investments	(114,017)	(402,284)	(162,437)
Changes in refundable deposits	96	5	(414)
Purchases of marketable securities	(83,379)	(46,458)	(37,952)
Sales and maturities of marketable securities	113,465	147,531	31,521
Non-operating distributions from co-investments	71,946	273,290	83,661
Net cash used in investing activities	(416,900)	(527,691)	(59,893)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	1,452,808	1,045,290	298,773
Payments on unsecured debt and mortgage notes	(916,209)	(1,026,616)	(230,398)
Proceeds from lines of credit	1,038,426	1,939,213	742,961
Repayments of lines of credit	(1,093,426)	(1,884,213)	(921,961)
Retirement of common stock	(269,315)	(56,989)	(51,233)
Additions to deferred charges	(13,772)	(10,898)	(4,250)
Payments related to debt prepayment penalties	(19,605)	(1,406)	0
Net proceeds from issuance of common stock	(296)	72,539	(919)
Net proceeds from stock options exercised	14,865	37,467	6,213
Payments related to tax withholding for share-based compensation	(5,664)	(3,688)	(869)
Distributions to noncontrolling interest	(30,990)	(27,993)	(29,050)
Redemption of noncontrolling interest	(3,113)	(36,568)	(1,333)
Redemption of redeemable noncontrolling interest	(872)	(73)	(144)
Common stock dividends paid	(536,098)	(507,754)	(484,182)
Net cash used in financing activities	(383,261)	(461,689)	(676,392)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	2,947	(70,301)	90,269
Unrestricted and restricted cash and cash equivalents at beginning of period	81,094	151,395	61,126
Unrestricted and restricted cash and cash equivalents at end of period	84,041	81,094	151,395
Supplemental disclosure of cash flow information:
Cash paid for interest, net of capitalized interest	211,732	194,418	203,803
Interest capitalized	14,615	24,169	18,708
Operating cash flows from operating leases	6,892	6,811	0
Supplemental disclosure of noncash investing and financing activities:
Issuance of Operating Partnership units for contributed properties	0	0	7,919
Issuance of DownREIT units in connection with acquisition of real estate	0	65,472	0
Transfers between real estate under development and rental properties, net	253,039	19,812	100,415
Transfer from real estate under development to co-investments	1,739	671	853
Reclassifications (from) to redeemable noncontrolling interest from additional paid in capital and noncontrolling interest	(4,299)	2,008	1,165
Redemption of redeemable noncontrolling interest via reduction of note receivable	0	0	4,751
Initial recognition of operating lease right-of-use assets	0	77,645	0
Initial recognition of operating lease liabilities	0	79,693	0
Debt assumed in connection with acquisition	0	143,006	45,804
Repayment of mortgage note from new financing proceeds	0	0	52,000
Essex Portfolio, L.P.
Cash flows from operating activities:
Net income	599,332	464,448	413,599
Adjustments to reconcile net income to net cash provided by operating activities:
Straight-lined rents	(19,426)	(1,218)	(347)
Depreciation and amortization	525,497	483,750	479,884
Amortization of discount on marketable securities	(19,075)	(28,491)	(17,637)
Amortization of (premium) discount and debt financing costs, net	6,674	5,689	(2,587)
Gain on sale of marketable securities	(2,131)	(1,271)	(737)
Provision for credit losses	687	0	0
Unrealized (gains) losses on equity securities recognized through income	(12,515)	(5,710)	5,159
Company's share of gain on the sales of co-investments	(2,225)	(51,097)	(10,569)
Earnings from co-investments	(64,287)	(61,039)	(78,563)
Operating distributions from co-investments	74,419	99,277	99,593
Accrued interest from notes and other receivables	(3,683)	(6,012)	(5,436)
Impairment loss	1,825	7,105	0
(Gain) loss on the sale of real estate and land	(64,967)	3,164	(61,861)
Equity-based compensation	8,157	7,010	7,135
Loss (gain) on early retirement of debt, net	22,883	(3,717)	0
Gain on remeasurement of co-investment	(234,694)	(31,535)	(1,253)
Changes in operating assets and liabilities:
Prepaid expenses, receivables, operating lease right-of-use assets, and other assets	(3,730)	6,969	(856)
Accounts payable, accrued liabilities, and operating lease liabilities	(10,382)	29,551	(145)
Other liabilities	749	2,206	1,175
Net cash provided by operating activities	803,108	919,079	826,554
Additions to real estate:
Acquisitions of real estate and acquisition related capital expenditures, net of cash acquired	(460,421)	(133,825)	(15,311)
Redevelopment	(48,980)	(70,295)	(73,000)
Development acquisitions of and additions to real estate under development	(108,781)	(158,234)	(182,772)
Capital expenditures on rental properties	(90,085)	(101,689)	(81,684)
Investments in notes receivable	(135,343)	(231,400)	0
Collections of notes and other receivables	98,711	168,720	29,500
Proceeds from insurance for property losses	723	3,734	1,408
Proceeds from dispositions of real estate	339,165	23,214	347,587
Contributions to co-investments	(114,017)	(402,284)	(162,437)
Changes in refundable deposits	96	5	(414)
Purchases of marketable securities	(83,379)	(46,458)	(37,952)
Sales and maturities of marketable securities	113,465	147,531	31,521
Non-operating distributions from co-investments	71,946	273,290	83,661
Net cash used in investing activities	(416,900)	(527,691)	(59,893)
Cash flows from financing activities:
Proceeds from unsecured debt and mortgage notes	1,452,808	1,045,290	298,773
Payments on unsecured debt and mortgage notes	(916,209)	(1,026,616)	(230,398)
Proceeds from lines of credit	1,038,426	1,939,213	742,961
Repayments of lines of credit	(1,093,426)	(1,884,213)	(921,961)
Retirement of common stock	(269,315)	(56,989)	(51,233)
Additions to deferred charges	(13,772)	(10,898)	(4,250)
Payments related to debt prepayment penalties	(19,605)	(1,406)	0
Net proceeds from issuance of common stock	(296)	72,539	(919)
Net proceeds from stock options exercised	14,865	37,467	6,213
Payments related to tax withholding for share-based compensation	(5,664)	(3,688)	(869)
Distributions to noncontrolling interest	(8,409)	(7,288)	(8,518)
Redemption of noncontrolling interest	(3,113)	(36,568)	(1,333)
Redemption of redeemable noncontrolling interest	(872)	(73)	(144)
Common stock dividends paid	(558,679)	(528,459)	(504,714)
Net cash used in financing activities	(383,261)	(461,689)	(676,392)
Net increase (decrease) in unrestricted and restricted cash and cash equivalents	2,947	(70,301)	90,269
Unrestricted and restricted cash and cash equivalents at beginning of period	81,094	151,395	61,126
Unrestricted and restricted cash and cash equivalents at end of period	84,041	81,094	151,395
Supplemental disclosure of cash flow information:
Cash paid for interest, net of capitalized interest	211,732	194,418	203,803
Interest capitalized	14,615	24,169	18,708
Operating cash flows from operating leases	6,892	6,811	0
Supplemental disclosure of noncash investing and financing activities:
Issuance of Operating Partnership units for contributed properties	0	0	7,919
Issuance of DownREIT units in connection with acquisition of real estate	0	65,472	0
Transfers between real estate under development and rental properties, net	253,039	19,812	100,415
Transfer from real estate under development to co-investments	1,739	671	853
Reclassifications (from) to redeemable noncontrolling interest from additional paid in capital and noncontrolling interest	(4,299)	2,008	1,165
Redemption of redeemable noncontrolling interest via reduction of note receivable	0	0	4,751
Initial recognition of operating lease right-of-use assets	0	77,645	0
Initial recognition of operating lease liabilities	0	79,693	0
Debt assumed in connection with acquisition	0	143,006	45,804
Repayment of mortgage note from new financing proceeds	$ 0	$ 0	$ 52,000